General psychology Part 1. Written by Dr. C George Boeree.


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General psychology Part 1. Written by Dr. C George Boeree. Psychology Department. Shippensburg University. USA

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General psychology Part 1. Written by Dr. C George Boeree.

  1. 1. Dr. C. George Boeree: General Psychology (1) E-Text Source: [ ] 1 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  2. 2. Dr. C. George Boeree: General Psychology (1) Index Index 2 Introduction 4 Neuropsychology 5 The Neuron 6 The Action Potential 10 Neurotransmitters 12 The Central Nervous System 14 Images of the Brain 16 The Emotional Nervous System 19 The Basal Ganglia 23 The Cerebrum 26 The Lobes 30 Methods 33 Qualitative Methods 34 Descriptive Statistics 36 Correlation 39 Experiments 42 Sensation and Perception 45 The Senses 46 Pain 52 Perception 54 2 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  3. 3. Dr. C. George Boeree: General Psychology (1) Emotion and Motivation 62 Emotion 63 Motivation 67 Hunger and Eating Disorders 71 Sleep 74 Sexuality 78 Sexual Orientation 86 Love 89 Learning and Memory 94 Learning 95 Memory 100 Pandemonium 104 "We cannot put off living until we are ready.... Life is fired at us point-blank." José Ortega y Gasset "We are all mortal until the first kiss and the second glass of wine." Eduardo Galeano "I like reality. It tastes of bread." Jean Anouilh "Cloquet hated reality but realized it was still the only place to get a good steak." Woody Allen 3 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  4. 4. Dr. C. George Boeree: General Psychology (1) Introduction Welcome to the General Psychology e-text! These pages were originally created for the students of my General Psychology classes at Shippensburg University. They deal with most of the issues covered in standard textbooks, but without the outrageous price tags. Psychology is the study of the mind, along with such aspects of mind as perception, cognition, emotion, and behavior. In some ways, it has only been around since the late 1800's, when people like Wilhelm Wundt, William James, and Sigmund Freud separated it from its various mother disciplines such as biology, philosophy, and medicine. But in other ways, it has been around as long as human beings have been discussing human beings. I suspect that cavemen and cavewomen probably sat around the fire talking about the same things we do: How come their kids are weird, why can't men and women get along better, what's with those folks from the next valley, how come old Zook hasn't been the same since that rock hit him, and what do dreams really mean. Today, Psychology tries to be a science. Science is the effort to study a subject with an explicit promise to think as logically and stick to the empirical facts as tightly as is humanly possible. Other sciences – chemistry, physics, biology, and so on – have had great success this way. Our cave-person ancestors would be astounded at our understanding of the world around us! But the subject matter of Psychology (and the other human sciences) is harder to pin down. We human beings are not as cooperative as some green goo in a test tube! It is a nearly impossible situation: To study the very thing that studies, to research the researcher, to psychoanalyze the psychoanalyst. So, as you will see, we still have a long way to go in Psychology. We have a large collection of theories about this part of being human or that part; we have a lot of experiments and other studies about one particular detail of life or another; we have many therapeutic techniques that sometimes work, and sometimes don't. But there is a steady progress that is easy to see for those of us with, say, a half century of life behind us. We are a bit like medicine in that regard: Don't forget that it wasn't really that long ago when we didn't have vaccines for simple childhood diseases, or anesthesia for operations; heart attacks and cancer were things people simply died of, as opposed to things that many people survive; and mental patients were people we just locked away or lobotomized! Some day – sooner rather than later, I think – we will have the same kinds of understanding of the human mind as we are quickly developing of the human body. The nice thing is, you and I can participate in this process! And this little e-text is as good a place to start as any. 4 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  5. 5. Dr. C. George Boeree: General Psychology (1) Neuropsychology 5 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  6. 6. Dr. C. George Boeree: General Psychology (1) Neurons It is clear that most of what we think of as our mental life involves the activities of the nervous system, especially the brain. This nervous system is composed of billions of cells, the most essential being the nerve cells or neurons. There are estimated to be as many as 100 billion neurons in our nervous system! A typical neuron has all the parts that any cell would have, and a few specialized structures that set it apart. The main portion of the cell is called the soma or cell body. It contains the nucleus, which in turn contains the genetic material in the form of chromosomes. Neurons have a large number of extensions called dendrites. They often look likes branches or spikes extending out from the cell body. It is primarily the surfaces of the dendrites that receive chemical messages from other neurons. One extension is different from all the others, and is called the axon. Although in some neurons, it is hard to distinguish from the dendrites, in others it is easily distinguished by its length. The purpose of the axon is to transmit an electro-chemical signal to other neurons, sometimes over a considerable distance. In the neurons that make up the nerves running from the spinal cord to your toes, the axons can be as long as three feet! Longer axons are usually covered with a myelin sheath, a series of fatty cells which have wrapped around an axon many times. These make the axon look like a necklace of sausage-shaped beads. They serve a similar function as the insulation around electrical wire. At the very end of the axon is the axon ending, which goes by a variety of names such as the bouton, the synaptic knob, the axon foot, and so on (I do not know why no one has settled on a consistent term!). It is there that the electro-chemical signal that has travelled the length of the axon is converted into a chemical message that travels to the next neuron. Between the axon ending and the dendrite of the next neuron is a very tiny gap called the synapse (or synaptic gap, or synaptic cleft), which we will discuss in a little bit. For every neuron, there are between 1000 and 10,000 synapses. 6 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  7. 7. Dr. C. George Boeree: General Psychology (1) The action potential When chemicals contact the surface of a neuron, they change the balance of ions (electrically charged atoms) between the inside and outside of the cell membrane. When this change reaches a threshold level, this effect runs across the cell's membrane to the axon. When it reaches the axon, it initiates the action potential. The surface of the axon contains hundreds of thousands of miniscule mechanisms called ion channels. When the charge enters the axon, the ion channels at the base of the axon allow positively charged ions to enter the axon, changing the electrical balance between inside and outside. This causes the next group of ion channels to do the same, while other channels return positive ions to the outside, and so on all the way down the axon. In this little diagram, the red represents the positive ions going into the axon, while the orange represents positive ions going out. The action potential travels at a rate of 1.2 to 250 miles per hour! This is, of course, over-simplified, but enough for our purposes. 7 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  8. 8. Dr. C. George Boeree: General Psychology (1) The synapse When the action potential reaches the axon ending, it causes tiny bubbles of chemicals called vesicles to release their contents into the synaptic gap. These chemicals are called neurotransmitters. These sail across the gap to the next neuron, where they find special places on the cell membrane of the next neuron called receptor sites. The neurotransmitter acts like a little key, and the receptor site like a little lock. When they meet, they open a passage way for ions, which then change the balance of ions on the outside and the inside of the next neuron. And the whole process starts over again. While most neurotransmitters are excitatory – i.e. they excite the next neuron – there are also inhibitory neurotransmitters. These make it more difficult for the excitatory neurotransmitters to have their effect. 8 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  9. 9. Dr. C. George Boeree: General Psychology (1) Types of Neurons While there are many different kinds of neurons, there are three broad categories based on function: 1. Sensory neurons are sensitive to various non-neural stimuli. There are sensory neurons in the skin, muscles, joints, and organs that indicate pressure, temperature, and pain. There are more specialized neurons in the nose and tongue that are sensitive to the molecular shapes we perceive as tastes and smells. Neurons in the inner ear provide us with information about sound. And the rods and cones of the retina allow us to see. 2. Motor neurons are able to stimulate muscle cells throughout the body, including the muscles of the heart, diaphragm, intestines, bladder, and glands. 3. Interneurons are the neurons that provide connections between sensory and motor neurons, as well as between themselves. The neurons of the central nervous system, including the brain, are all interneurons. Most neurons are collected into "packages" of one sort or another, often visible to the naked eye. A clump of neuron cell bodies, for example, is called a ganglion (plural: ganglia) or a nucleus (plural: nuclei). A fiber made up of many axons is called a nerve. In the brain and spinal cord, areas that are mostly axons are called white matter, and it is possible to differentiate pathways or tracts of these axons. Areas that include large number of cell bodies are called gray matter. 9 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  10. 10. Dr. C. George Boeree: General Psychology (1) The Action Potential The movement of a signal through the neuron and its axon is all about ions. An ion is a charged particle, such as Na+, the sodium ion. It has a positive charge, because it is missing one electron. Other ions, of course, are negatively charged. Cells have membranes that are made of lipid molecules (fats), and they prevent most things from entering or leaving the cell. But all over a cell membrane are proteins that stick out on both sides of the cell membrane. Some of these are ion channels. Most ion channels simply allow ions to flow in or out of the cell. When we draw diagrams, we usually picture these channels as if they were little holes in the cell membrane. They are, as I said, really complex proteins. When an ion attaches itself to one of these proteins, the protein changes shape, and in doing so carries the ion to the other side of the membrane, where it is released. The normal tendency is for everything inside and outside a cell to balance out this way: If there is too much of a chemical on one side, it flows to the other, until there's a balance; If there are too many positive or negative ions on one side, they tend to move to the other side, until there's a balance. Some channels are called gates. They can, depending on their environment, open or close. For some, it's a matter of what chemicals attach themselves to a part of the gate. For others, it's a change in the positive-negative balance that causes them to open or close. In the neuron, there are many such gates, including sodium gates and potassium gates. Both of these respond to positive-negative balance changes. One example of a chemical gate are the receptor sites on the dendrites of a neuron: When a chemical called a neurotransmitter attaches itself to a spot on the gate, the gate opens up to allow sodium ions into the cell. Other ion channels are called pumps. They use energy supplied by the cell to actually pump ions in or out of the cell, by force if you will. The best examples are the sodiumpotassium pumps on the neuron's membranes. These pumps push sodium ions out of the cell, and potassium ions (K+) into the cell. They are actually maintaining an imbalance of these chemicals. If you are alert, you notice that both the sodium and the potassium ions are positive. Neurons actually have a pretty strong negative charge inside them, in contrast to a positive charge outside. This is due to other molecules called anions. They are negatively charged, but are way too big to leave through any channel. 10 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  11. 11. Dr. C. George Boeree: General Psychology (1) They stay put and give the cell a negative charge inside. So, when an axon is at rest, the anions give it a negative charge, the sodium pumps keep sodium out and potassium in, and the sodium gates and potassium gates are all closed. Because of the positive-negative difference between the inside and outside, this resting state is called a resting potential. The word potential refers to the fact that there is a potential for change here. We use the same term to refer to a battery that is just sitting there, not connected to anything: It, too, has a resting potential. When changes occurring in the membranes of the dendrites and the body of the cell reach the axon, the sodium gates respond: some of them open and let sodium ions in, so that the inside starts to become less negative. If this reaches a certain level, called a threshold, more sodium gates respond and let more ions in... Then we have what is called the action potential – a moving exchange of ions that runs along the length of the axon. So many sodium ions get in that, for a very short time, the difference between the outside and inside of the cell is actually reversed: The inside is positive and the outside negative. Then the situation changes: The sodium gates close and the potassium gates open up. Potassium rushes out of the cell, which brings the charge inside the cell back down to where it was – negative on the inside, positive on the outside. Notice, though, that the sodium is now inside the cell and the potassium is outside, that is, they are in the wrong places. So, the sodium-potassium pumps get back to work and pump the sodium back out and the potassium back in, and things are back to where we started. Now all this happens at one little segment of the axon at a time: Sodium goes in at section one; that triggers the potassium to start going out at section one and the sodium to start coming in at section two; that in turn triggers the potassium to go out at section two and the sodium to come in at section three; and so on – like a row of dominos going down. In this little graphic, representing an axon, the red represents sodium flowing in and the orange represents the potassium flowing out: [ animated image at ] The myelin sheath around many axons speeds up this process considerably: Instead of one tiny segment triggering action at the very next little segment, the changes "jump" from one gap in the sheath to the next. This is called saltatory conduction, from the Latin word for "jump" (also seen in words like somersault). When the action potential reaches the axon ending, it causes another ion (calcium, Ca++) to enter the cell, which in turn causes the vesicles – the tiny bubbles full of neurotransmitters – to release their contents into the synaptic gap.... Amazing, isn't it? 11 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  12. 12. Dr. C. George Boeree: General Psychology (1) Neurotransmitters Neurotransmitters are the chemicals which account for the transmission of signals from one neuron to the next across synapses. They are also found at the axon endings of motor neurons, where they stimulate the muscle fibers to contract. And they and their close relatives are produced by some glands such as the pituitary and the adrenal glands. In this chapter, we will review some of the most significant neurotransmitters. Acetylcholine was the first neurotransmitter to be discovered. It was isolated in 1921 by a German biologist named Otto Loewi, who would later win the Nobel Prize for his work. Acetylcholine has many functions: It is responsible for much of the stimulation of muscles, including the muscles of the gastro-intestinal system. It is also found in sensory neurons and in the autonomic nervous system, and has a part in scheduling REM (dream) sleep. The well-known poison botulin works by blocking acetylcholin, causing paralysis. The botulin derivative botox is used by many people to temporarily eliminate wrinkles –a sad commentary on our times, I would say. On a more serious note, there is a link between acetylcholine and Alzheimer's disease: There is something on the order of a 90% loss of acetylcholine in the brains of people suffering from that debilitating disease. In 1946, a Swedish biologist by the name of Ulf von Euler discovered norepinephrine (formerly called noradrenalin). He also won a Nobel Prize. Norepinephrine is strongly associated with bringing our nervous systems into "high alert." It is prevalent in the sympathetic nervous system, and it increases our heart rate and our blood pressure. Our adrenal glands release it into the blood stream, along with its close relative epinephrine (aka adrenalin). It is also important for forming memories. Stress tends to deplete our store of adrenalin, while exercise tends to increase it. Amphetamines ("speed") work by causing the release of norepinephrine. Another relative of norepinephrine and epinephrine is dopamine, discovered to be a neurotransmitter in the 1950s by another Swede, Arvid Carlsson. It is an inhibitory nruotransmitter, meaning that when it finds its way to its receptor sites, it blocks the tendency of that neuron to fire. Dopamine is strongly associated with reward mechanisms in the brain. Drugs like cocaine, opium, heroin, and alcohol increase the levels of dopamine, as does nicotine! The severe mental illness schizophrenia has been shown to involve excessive amounts of dopamine in the frontal lobes, and drugs that block dopamine are used to help schizophrenics. On the other hand, too little dopamine in the motor areas of the brain are responsible for Parkinson's disease, which involves uncontrollable muscle tremors. It was the same Arvid Carlsson mentioned above who figured out that the precursor to dopamine (L-dopa) could eleviate some ot the symptoms. He was awarded the Nobel Prize in 2000. In 1950, Eugene Roberts and J. Awapara discovered GABA (gamma aminobutyric acid), which is another kind of inhibitory neurotransmitter. GABA acts like a brake to the excitatory neurotransmitters that lead to anxiety. People with too little GABA tend to suffer from anxiety disorders, and drugs like Valium work by enhancing the effects of GABA. If GABA is lacking in some parts of the brain, epilepsy results. Glutamate is an excitatory relative of GABA. It is the most common neurotransmitter in the central nervous system – as much as half of all neurons in the brain – and is especially important in regards to memory. Curiously, glutamate is actually toxic to neurons, and an excess will kill them. Sometimes brain damage or a stroke will lead to an excess and end with many more brain cells dying than from the original trauma. ALS, more commonly known as Lou Gehrig's disease, results from excessive glutamate production. Many believe it may also be responsible for quite a variety of diseases of the nervous system, and are looking for ways to 12 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  13. 13. Dr. C. George Boeree: General Psychology (1) minimize its effects Glutamate was discovered by Kikunae Ikeda of Tokay Imperial Univ. in 1907, while looking for the flavor common to things like cheese, meat, and mushrooms. He was able to extract an acid from seaweedglutamate. He went on to invent the well known seasoning MSG - monosodium glutamate. It took decades for Peter Usherwood to identify glutamate as a nurotransmitter in locusts in 1994. Serotonin has been found to be intimately involved in emotion and mood. Too little serotonin has been shown to lead to depression, problems with anger control, obsessive-compulsive disorder, and suicide. Too little also leads to an increased appetite for carbohydrates (starchy foods) and trouble sleeping, which are also associated with depression and other emotional disorders. Vittorio Erspamer first discovered what we now call seratonin in the 1930s. It was found in blood serum in 1948 by Irvine Page, who named it serotonin (from "serum-tonic”). Another researcher in Page’s lab Maurice Rapport - proved that it was an amine. John Welsh found that it was a neurotransmitter in molluscs in 1954, and Betty Twarog (also at Page's lab) found it in vertebrates in 1952. All this gives you a sense of the cooperative nature of most of scientific discovery! Prozac and other recent drugs help people with depression by preventing the neurons from "vacuuming" up excess seratonin, so that there is more floating around in the synapses. It is interesting that a little warm milk before bedtime also increases the levels of seratonin. As mom may have told you, it helps you to sleep. Serotonin is a derivative of tryptophan, which is found in milk. The "warm" part is just for comfort! On the other hand, serotonin also plays a role in perception. Hallucinogens such as LSD work by attaching to seratonin receptor sites and thereby blocking transmissions in perceptual pathways. In 1973, Solomon Snyder and Candace Pert of Johns Hopkins discovered endorphin. Endorphin is short for "endogenous morphine," i.e. built-in heroin! It is structurally very similar to the opioids (opium, morphine, heroin, etc.) and has similar functions: It is involved in pain reduction and pleasure, and the opioid drugs work by attaching to endorphin's receptor sites. It is also the neurotransmitter that allows bears and other animals to hibernate. Consider: Heroin slows heart-rate, respiration, and metabolism in general – exactly what you would need to hibernate. Of course, sometimes heroin slows it all down to nothing: Permanent hibernation. 13 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  14. 14. Dr. C. George Boeree: General Psychology (1) The Central Nervous System The Spinal Cord The spinal cord runs from the base of the skull all the way down the spine to the "tail bone." The neurons are found in an H-shaped space within the spinal vertebrae. There are motor pathways coming down from the brain and sensory pathways going up to the brain. Sensory nerves enter into the back parts (dorsal roots) of the "H," while motor neurons exit the forward parts (ventral roots) of the "H." Interneurons often connect these sensory and motor neurons. Besides sending messages up and down to and from the brain, the spinal cord has another very important function: Reflexes. In fact, in very simple animals, that is the main function of the cord. Basically, a reflex is the connection of sensory neurons, via interneurons, to motor neurons. For example, there are pain sensors in your fingers. If you hold your finger over a flame for a period of time, the pain will trigger motor neurons to pull your finger away. It is true that you can over-ride this reflex with "will power," but as the example intentionally shows, it isn't easy! Reflexes do much more than just get your finger out of the fire: A great deal of movement is accomplished through reflexes. Even brand new babies already have the necessary reflexes for walking: If you hold a baby and gently touch its feet to the floor, it will start making step-like movements! All that is needed is the muscle strength to stand and, of course, a lot of practice. The Brain The brain is traditionally divided into three parts, the hindbrain, the midbrain, and the forebrain. This drawing is roughly what it would look like if you sliced your brain straight down the middle, like a part in your hair. The front of the brain is on the left, the back on the right: The hindbrain or brain stem consists of three parts. The first is the medulla, which is actually an extension of the spinal cord into the skull. Besides containing tracts up and down to and from the higher portions of the brain, the medulla also contains some of the essential nuclei that govern respiration and heart rate. The upper part of the medulla contains a pinky-sized complex of nuclei called the reticular formation. It is the regulatory system for sleep, waking, and alertness. The second part is the pons, which means bridge in Latin. It is primarily the pathways connecting the two halves of the next part, which is called the cerebellum. 14 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  15. 15. Dr. C. George Boeree: General Psychology (1) The cerebellum, which means "little brain" in Latin, is in fact shaped like a small brain, and it is primarily responsible for coordinating involuntary movement. It is believed that, when you learn complex motor tasks, the details are recorded in the cerebellum. The midbrain is, in human beings, the smallest part of the brain. It connects the hindbrain to the forebrain, and contains several pathways important to hearing and vision. It is much larger in lower animals as well as in the human fetus. The largest and, for psychologists, most interesting part of the brain is the forebrain. It starts with the thalamus, which is practically in the center of your head. The thalamus is like a switching station, conducting signals from the body up to the relevant parts of the higher brain, and down from the brain to the lower brain and spinal cord. The forebrain, though, is complex enough to require its own chapter – two, in fact: One for the limbic system, and one for the cerebrum. 15 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  16. 16. Dr. C. George Boeree: General Psychology (1) Images of the Brain* * Images from The Virtual Hospital (all labeling errors my own!) 16 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  17. 17. Dr. C. George Boeree: General Psychology (1) Before the 20th century, there was only one way to see the brain: Open up the skull. Of course, with the assistance of a talented medical artist or, later, a good photograph, this provides us with a particularly good view. For the most part, however, it required a dead patient! Fortunately, we now have a number of imaging techniques that allow us to see what is going on inside the brain of a living human being. X-rays were the first things used to look at a living brain. While some details are visible, the nature of the brain is such that it is not a particularly good subject for the X-ray. The CT scan (computer tomography) or CAT scan involves taking a large series of x-rays from various angles, and then combining them into a threedimensional record on a computer. The image can be displayed and manipulated on a computer screen. 17 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  18. 18. Dr. C. George Boeree: General Psychology (1) The PET scan (positron emission tomography) works like this: The doctor injects radioactive glucose (that’s sugar water) into the patient’s bloodstream. The device then detects the relative activity level – that is, the use of glucose – of different areas of the brain. The computer generates an image that allows the researcher to tell which parts of the brain are most active when we perform various mental operations, whether it’s looking at something, counting in our heads, imagining something, or listening to music! The MRI (magnetic resonance imaging) works like this: You create a strong magnetic field which runs through the person from head to toe. This causes the spinning hydrogen atoms in the person’s body to line up with the magnetic field. Then you send a radio pulse at a special frequency that causes the hydrogen protons to spin in a different direction. When you turn off the radio pulse, the protons will return to their alignment with the magnetic field, and release the extra energy they took in from the radio pulse. That energy is picked up by the same coil that produced the energy, now acting like a three dimensional antenna. Since different tissues have different relative amounts of hydrogen in them, they give a different density of energy signals, which the computer organizes into a detailed three-dimensional image. This image is nearly as detailed as an anatomical photograph! 18 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  19. 19. Dr. C. George Boeree: General Psychology (1) The Emotional Nervous System Emotion involves the entire nervous system, of course. But there are two parts of the nervous system that are especially significant: The limbic system and the autonomic nervous system. The Limbic System The limbic system is a complex set of structures that lies on both sides and underneath the thalamus, just under the cerebrum. It includes the hypothalamus, the hippocampus, the amygdala, and several other nearby areas. It appears to be primarily responsible for our emotional life, and has a lot to do with the formation of memories. In this drawing, you are looking at the brain cut in half, but with the brain stem intact. The part of the limbic system shown is that which is along the left side of the thalamus (hippocampus and amygdala) and just under the front of the thalamus (hypothalamus): Hypothalamus The hypothalamus is a small part of the brain located just below the thalamus on both sides of the third ventricle. (The ventricles are areas within the cerebrum that are filled with cerebrospinal fluid, and connect to the fluid in the spine.) It sits just inside the two tracts of the optic nerve, and just above (and intimately connected with) the pituitary gland. The hypothalamus is one of the busiest parts of the brain, and is mainly concerned with homeostasis. Homeostasis is the process of returning something to some "set point.” It works like a thermostat: When your room gets too cold, the thermostat conveys that information to the furnace and turns it on. As your room warms up and the temperature gets beyond a certain point, it sends a signal that tells the furnace to turn off. The hypothalamus is responsible for regulating your hunger, thirst, response to pain, levels of pleasure, sexual satisfaction, anger and aggressive behavior, and more. It also regulates the functioning of the parasympathetic and sympathetic nervous systems, which in turn means it regulates things like pulse, blood pressure, breathing, and arousal in response to emotional circumstances. The hypothalamus receives inputs from a number of sources. From the vagus nerve, it gets information about blood pressure and the distension of the gut (that is, how full your stomach is). From the reticular formation in the brainstem, it gets information about skin temperature. From the optic nerve, it gets information about light and darkness. From unusual neurons lining the ventricles, it gets information about the contents of the cerebrospinal fluid, including toxins that lead to vomiting. And from the other parts of the limbic system and the olfactory (smell) nerves, it gets information that helps regulate eating and sexuality. The hypothalamus also has some receptors of its own, that provide information about ion balance and temperature of the blood. In one of the more recent discoveries, it seems that there is a protein called leptin which is released by fat 19 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  20. 20. Dr. C. George Boeree: General Psychology (1) cells when we overeat. The hypothalamus apparently senses the levels of leptin in the bloodstream and responds by decreasing appetite. It would seem that some people have a mutation in a gene which produces leptin, and their bodies can’t tell the hypothalamus that they have had enough to eat. However, many overweight people do not have this mutation, so there is still a lot of research to do! The hypothalamus sends instructions to the rest of the body in two ways. The first is to the autonomic nervous system. This allows the hypothalamus to have ultimate control of things like blood pressure, heartrate, breathing, digestion, sweating, and all the sympathetic and parasympathetic functions. The other way the hypothalamus controls things is via the pituitary gland. It is neurally and chemically connected to the pituitary, which in turn pumps hormones called releasing factors into the bloodstream. As you know, the pituitary is the so-called "master gland,” and these hormones are vitally important in regulating growth and metabolism. Hippocampus The hippocampus consists of two "horns” that curve back from the amygdala. It appears to be very important in converting things that are "in your mind” at the moment (in short-term memory) into things that you will remember for the long run (long-term memory). If the hippocampus is damaged, a person cannot build new memories, and lives instead in a strange world where everything they experience just fades away, even while older memories from the time before the damage are untouched! This very unfortunate situation is fairly accurately portrayed in the wonderful movie Memento. Amygdala The amygdalas are two almond-shaped masses of neurons on either side of the thalamus at the lower end of the hippocampus. When it is stimulated electrically, animals respond with aggression. And if the amygdala is removed, animals get very tame and no longer respond to things that would have caused rage before. But there is more to it than just anger: When removed, animals also become indifferent to stimuli that would have otherwise have caused fear and even sexual responses. Related areas Besides the hypothalamus, hippocampus, and amygdala, there are other areas in the structures near to the limbic system that are intimately connected to it: • The cingulate gyrus is the part of the cerebrum that lies closest to the limbic system, just above the corpus collosum. It provides a pathway from the thalamus to the hippocampus, seems to be responsible for focusing attention on emotionally significant events, and for associating memories to smells and to pain. • The septum, which lies in front of the thalamus, has areas that seem to be centers for orgasm. • The ventral tegmental area of the brain stem (just below the thalamus) consists of dopamine pathways that seem to be responsible for pleasure. People with damage here tend to have 20 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  21. 21. Dr. C. George Boeree: General Psychology (1) difficulty getting pleasure in life, and often turn to alcohol, drugs, sweets, and gambling. • The basal ganglia (including the caudate nucleus, the putamen, the globus pallidus, and the substantia nigra) lie over and to the sides of the limbic system, and are tightly connected with the cortex above them. They are responsible for repetitive behaviors, reward experiences, and focusing attention. If you are interested in learning more [see chapter on Basal Ganglia]. • The prefrontal cortex, which is the part of the frontal lobe which lies in front of the motor area, is also closely linked to the limbic system. Besides apparently being involved in thinking about the future, making plans, and taking action, it also appears to be involved in the same dopamine pathways as the ventral tegmental area, and plays a part in pleasure and addiction. The Autonomic Nervous System The second part of the nervous system to have a particularly powerful part to play in our emotional life is the autonomic nervous system. The autonomic nervous system is composed of two parts, which function primarily in opposition to each other. The first is the sympathetic nervous system, which starts in the spinal cord and travels to a variety of areas of the body. Its function appears to be preparing the body for the kinds of vigorous activities associated with "fight or flight,” that is, with running from danger or with preparing for violence. Activation of the sympathetic nervous system has the following effects: dilates the pupils opens the eyelids stimulates the sweat glands dilates the blood vessels in large muscles constricts the blood vessels in the rest of the body increases the heart rate opens up the bronchial tubes of the lungs inhibits the secretions in the digestive system One of its most important effects is causing the adrenal glands to release epinephrine (aka adrenalin) into the blood stream. Epinephrine is a powerful hormone that causes various parts of the body to respond in much the same way as the sympathetic nervous system. Being in the blood stream, it takes a bit longer to stop its effects. This is why, when you get upset, it sometimes takes a while before you can calm yourself down again! The sympathetic nervous system also takes in information, mostly concerning pain from internal organs. Because the nerves that carry information about organ pain often travel along the same paths that carry information about pain from more surface areas of the body, the information sometimes get confused. This is called referred pain, and the best known example is the pain some people feel in the shoúlders and arms when they are having a heart attack. The other part of the autonomic nervous system is called the parasympathetic nervous system. It has its roots in the brainstem and in the spinal cord of the lower back. Its function is to bring the body back from the emergency status that the sympathetic nervous system puts it into. Some of the details of parasympathetic arousal include... pupil constriction activation of the salivary glands stimulating the secretions of the stomach 21 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  22. 22. Dr. C. George Boeree: General Psychology (1) stimulating the activity of the intestines stimulating secretions in the lungs constricting the bronchial tubes decreasing heart rate The parasympathetic nervous system also has some sensory abilities: It receives information about blood pressure, levels of carbon dioxide in the blood, and so on. There is actually one more part of the autonomic nervous system that we don't mention too often: The enteric nervous system. This is a complex of nerves that regulate the activity of the stomach! When you get sick to your stomach or feel butterflies when you get nervous, you can blame the enteric nervous system. 22 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  23. 23. Dr. C. George Boeree: General Psychology (1) The Basal Ganglia The basal ganglia are a collection of nuclei found on both sides of the thalamus, outside and above the limbic system, but below the cingulate gyrus and within the temporal lobes. Although glutamate is the most common neurotransmitter here as everywhere in the brain, the inhibitory neurotransmitter GABA plays the most important role in the basal ganglia. The largest group of these nuclei are called the corpus striatum ("striped body"), made up of the caudate nucleus ("tail"), the putamen ("shell"), the globus pallidus ("pale globe"), and the nucleus accumbens ("leaning"). All of these structures a double ones, one set on each side of the central septum. The caudate begins just behind the frontal lobe and curves back towards the occipital lobe. It sends its messages to the frontal lobe (especially the orbital cortex, just above the eyes), and appears to be responsible for informing us that something is not right and we should do something about it: Wash your hands! Lock your door! As these examples are meant to suggest, obsessive compulsive disorder (OCD) is likely to involve an overactive caudate. On the other hand, an underactive caudate may be involved in various disorders, such as ADD, depression, aspects of schizophrenia, and just plain lethargy. It is also involved in PAP syndrome, a dramatic loss of motivation only recently discovered (see below). The putamen lies just under and behind the front of the caudate. It appears to be involved in coordinating automatic behaviors such as riding a bike, driving a car, or working on an assembly line. Problems with the putamen may account for the symptoms of Tourette's syndrome. The globus pallidus is located just inside the putamen, with an outer part and an inner part. It receives inputs from the caudate and putamen and provides outputs to the substantia nigra (below). The nucleus accumbens is a nucleus just below the previous nuclei. It receives signals from the prefrontal cortex (via the ventral tegmental area) and sends other signals back there via the globus pallidus. The inputs use dopamine, and many drugs are known to greatly increase these messages to the nucleus accumbens. Another nucleus of the basal ganglia is the substantia nigra ("black substance"). Located in the upper portions of the midbrain, below the thalamus, it gets its color from neuromelanin, a close relative of the skin pigment. One part (the pars compacta) uses dopamine neurons to send signals up to the striatum. The exact function isn't known, but is believed to involve reward circuits. Also, Parkinson's disease is due to the death of dopamine neurons here. The other part of the substantia nigra (the pars reticulata) is mostly GABA neurons. It's main known function is controlling eye movements. It is also involved in Parkinson's, as well as epilepsy. 23 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  24. 24. Dr. C. George Boeree: General Psychology (1) As you can see, quite a few serious problems are strongly associated with the basal ganglia. Some, such as ADHD, Tourette's, obsessive-compulsive disorder, and schizophrenia, will be covered in other parts of this text. Others are somewhat less psychological and more physical, but are still important.... Parkinson's disease Parkinson's is characterized by tremor (shaking), rigid muscles, difficulty making quick, smooth movements, and difficulty standing and walking. Many people also develop depression and anxiety and, later in life, problems with memory loss and dementia. It usually develops late in life, but it can occur in younger people. One well-known case is the actor Michael J. Fox. It is very difficult for both the patient and his or her family. Parkinson's is originates in the death of cells in the substantia nigra and the loss of dopamine and melanin produced by those cells. It progresses to other parts of the basal ganglia and to the nerves that control the muscles, involving other neurotransmitters. Possible causes or contributing factors include environmental toxins, head trauma, and genetics. There are treatments available that slow the course of Parkinson's and alleviate the symptoms. Most involve replacing or mimicking the lost dopamine and other neurotransmitters. Unfortunately, the disease slowly progresses to where the treatments only work for a few hours at a time. Parkinson's does not directly cause death and many patients live long lives with it. Huntington's disease Huntington's is characterized by loss of memory and odd jerking movements called chorea ("dance"). It is a hereditary disease (with a dominant gene) involving cell death in the caudate nucleus. It usually starts in a person's 30s, but may start at any age. There is no cure, but there are treatments that can reduce the symptoms. It is fatal, although it is complications of the disease that usually cause death, rather than the disease itself. Many Huntington's sufferers commit suicide. Cerebral palsy People with cerebral palsy have various motor problems, such as spasticity, paralysis, and even seizures. Spasticity is where some muscles are constantly tight and so interfere with normal movement. This is the reason for the unusual hand and arm positions most of us have seen in people with cerebral palsy. It is apparently due to brain damage, usually sometime before birth. Causes may include fetal infection, environmental toxins, or lack of oxygen. Although cerebral palsy tends to remain relatively stable throughout life, there is no cure and is very difficult to deal with for both the person and his or her family. 24 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  25. 25. Dr. C. George Boeree: General Psychology (1) PAP ( or Athymhormic) syndrome PAP is characterized by an unusual lack of motivation. A dramatic case was that of Mr. M, who, while drowning, simply failed to try to save himself, even though a good swimmer. Damage to the caudate nucleus means that nothing carries any emotional significance anymore. Drowning? Don't be concerned. People with PAP also ignore the usual social and moral motivations we all take for granted. They don't quite "get" that their lack of action could have significant consequences. Without the motivating influence of the basal ganglia, the frontal lobe simply stops planning for the future. Oddly, they can still respond to external motivation, such as a loved one's request or an authority's command. See the April 2005 Scientific American Mind article by Patrick Verstichal and Pascal Larrouy for more on PAP syndrome. 25 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  26. 26. Dr. C. George Boeree: General Psychology (1) The Cerebrum The cerebrum – which is just Latin for "brain" – is the newest (evolutionarily) and largest part of the brain as a whole. It is here that things like perception, imagination, thought, judgment, and decision occur. The surface of the cerebrum – the cerebral cortex – is composed of six thin layers of neurons, which sit on top of a large collection of white matter pathways. The cortex is heavily convoluted, so that if you were to spread it out, it would actually take up about 2 1/2 square feet (2500 sq cm). It includes about 10 billion neurons, with about 50 trillion synapses! The convolutions have "ridges" which are called gyri (singular: gyrus), and "valleys" which are called sulci (singular: sulcus). Some of the sulci are quite pronounced and long, and serve as convenient boundaries between four areas of the cerebrum called lobes. The furthest forward is the frontal lobe (from the Latin word for forehead). It seems to be particularly important: This lobe is responsible for voluntary movement and planning and is thought to be the most significant lobe for personality and intelligence. At the back portion of the frontal lobe, along the sulcus that separates it from the parietal lobe, is an area called the motor cortex. In studies with brain surgery patients, stimulating areas of the motor cortex with tiny electrical probes caused movements. It has been possible for researchers to actually map out the motor cortex quite precisely. The lowest portions of the motor cortex, closest to the temples, control the muscles of the mouth and face. The portions of the motor cortex near the top of the head control the legs and feet. Behind the frontal lobe is the parietal lobe (from a Latin word meaning wall). It includes an area called the somatosensory cortex, just behind the sulcus separating this lobe from the frontal lobe. Again, doctors stimulating points of this area found their patients describing sensations of being touched at various parts of their bodies. Just like the motor cortex, the somatosensory cortex can be mapped, with the mouth and face closest to the temples and the legs and feet at the top of the head. 26 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  27. 27. Dr. C. George Boeree: General Psychology (1) At the side of the head is the temporal lobe (from the Latin word for temple). The special area of the temporal lobe is the auditory cortex. As the name says, this area is intimately connected with the ears and specializes in hearing. It is located near to the temporal lobe's connections with the parietal and frontal lobes. At the back of the head is the occipital lobe. At the very back of the occipital lobe is the visual cortex, which receives information from the eyes and specializes, of course, in vision. The areas of the lobes that are not specialized are called association cortex. Besides connecting the various sensory and motor cortices, this is also believed to be where our thought processes occur and many of our memories are ultimately stored. The Hemispheres If you look at the brain from the top, it becomes immediately obvious that it is split in two from front to back. There are, in fact, two hemispheres, almost as if we have two brains in our heads instead of just one. 27 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  28. 28. Dr. C. George Boeree: General Psychology (1) Of course, these two halves are intimately linked together with an arch of white matter called the corpus callosum. In various ways, researchers have discovered that the two halves do have some specialization. It is the left hemisphere that relates to the right side of the body (generally), and the right hemisphere that relates to the left side of the body. Also, it is the left hemisphere that usually has language, and seems to be primarily responsible for similar systems such as math and logic. The right hemisphere has more to do with things like spatial orientation, face recognition, and body image. It also seems to govern our ability to appreciate art and music. Some of the most interesting work done concerning the two hemispheres was done by Roger Sperry. He worked with people who had had a pretty serious operation to control their epilepsy. It seems that, in some cases, severe epilepsy could be nearly eliminated by cutting the corpus callosum. In a sense, these people really did have two brains (or cerebrums, to be accurate)! For example, Sperry found that if he put something in the right hand of one of these people after they had their operation, they could say what it was. But if he put it in their left hand, they could not. This is easy to understand: The feeling of the thing in the right hand goes to the left hemisphere and, since that's the side with language, the person could say what it was. The feeling of the thing in the left hand, though, went to the right hemisphere, which can't do much talking. The eyes are hooked up to the hemispheres in a somewhat complicated way: The right hand side of each retina (which sees things to the left of a focus point) goes to the right hemisphere, and the left hand side of each retina (which see things to the right) goes to the left hemisphere. What this means is that, if you have someone stare at a focus point and briefly show them something on the left, it is the right hemisphere that receives the information. If you show them something on the right, it is the left hemisphere that receives the information. Sperry would flash things on a projection screen and ask the patients to either say what they saw or pick what they saw with one hand or the other from a box full of things. So, if he showed a ball on the left side of the screen and a pencil on the right, the person would say "pencil" (using the left hemisphere's speech centers) but pick a ball from the box with his or her left hand (using the right hemisphere)! There were many interesting anecdotes that came out of his research. For example, it turns out that, though the left hemisphere has speech, it is pretty bad at drawing. The right hemisphere, controlling the left hand, could still draw quite well. He had the patients try little puzzles. One man, struggling to do the puzzle with his right hand, couldn't keep his left hand from trying to jump in to help! With one young woman, he flashed a picture of a naked man on the right side of the screen. She blushed and giggled, but when asked, couldn't say why. Of course, only the right hemisphere had seen the picture, and the left hemisphere had not! 28 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  29. 29. Dr. C. George Boeree: General Psychology (1) Fortunately for these people, these situations don't come up much in ordinary life, so they didn't feel terribly confused most of the time. Most of us, of course, have an intact corpus callosum, and the two halves of our brains are in constant communication. Speech So, speech is predominantly a function of the left hemisphere. Actually, the right hemisphere does have a little bit of speech, too: It has a good grasp of names and curse words! In addition, if you have brain damage to the left hemisphere early enough in childhood, the right hemisphere will take over the speech function. And it seems that there are some people who have language on the right or even on both sides. It is interesting to consider that monkeys and apes appear to sensitive to calls of their own species in the left hemisphere: They will turn their right ears towards the sound! Even some song birds, such as canaries, have hemispheric specialization. One of the earliest things discovered about the brain were the speech centers. One is called Broca's area, after the doctor who first discovered it. It is located at the bottom of the left frontal lobe. A patient who had had damage to this area lost his ability to speak, which is called expressive aphasia. Another area is Wernicke's area, which is nearby Broca's area but in the temporal lobe, right next to the auditory cortex. This is were we understand the meaning of speech, and damage to this area will leave you with receptive aphasia, meaning that you will be unable to understand what is being said to you. Occasionally, someone has damage to the connections between Broca's and Wernicke's areas. This leads to conduction aphasia. Someone with this problem can understand speech just fine, and can produce it as well. They just can't repeat something they just heard! Another important area is the angular gyrus, just above and behind Wernicke's area. It serves as the connection between the language centers and the visual cortex. If this area is damaged, the person will suffer from alexia (inability to read) and agraphia (inability to write). 29 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  30. 30. Dr. C. George Boeree: General Psychology (1) The Lobes The Frontal Lobe Starting from the central sulcus and working forward, we first have the motor cortex, which sends its signals down to the body to control the skeletal muscles. Just in front of the motor cortex there is the premotor cortex, which is where we compose and rehearse movements before we engage in them. Broca's area for speech production is part of the premotor cortex. And then we have the prefrontal cortex, where some of the most interesting things occur. Some say that will power, our sense of reality, and our sense of our own personality reside there. A few areas of the prefrontal cortex are at least partially understood. The dorsolateral area (high and to the sides) appears to allow us to hold ideas in awareness, focus on them, and even manipulate them. The ventromedial area (low and close to the midline) seems to be involved in emotional experience and provides us with the feeling that things make sense and have meaning. Low levels of activity here are associated with depression: Nothing makes any sense. High levels, on the other hand, are associated with mania: Every little thing is full of importance! The orbital area of the prefrontal cortex (just above the eyeballs) tells us when something is wrong and requires serious attention. It also has the ability to inhibit behaviors that are inappropriate, such as those that are harmful to us or are socially unacceptable. This includes the ability to counteract the signals for aggression from the amygdala in the limbic system. It is believed that many violent criminals have had damage to this area of the brain. In the most frontal part of the prefrontal lobe is an area devoted to interpreting people's intentions and motives. Autistic people seem to have some sort of defect in this location. The Temporal Lobe This lobe sits at the two sides of the head, under the temples. The upper part of the temporal lobe, along the Sylvian fissure that separates it from the frontal lobe, is the primary auditory cortex, which receives input from cochlea. The areas around it are devoted to interpreting sounds, and one of these in particular (Wernicke's area, toward the boundary with the parietal lobe in the left hemisphere) is known to be devoted to the understanding of language. Another area is called the fusiform gyrus, which sits low in the temporal lobe near the occipital lobe. In the left hemisphere, it is responsible for word and number recognition. In the right hemisphere, it is responsible for the crucial human ability to recognize faces. Problems here leave one with a disorder called prosopagnosia, which makes social life very difficult. There are medial (inner) areas of the temporal lobes that are closely connected to the hippocampus and appear to be devoted to memory for life events (episodic memory). One very odd function of the temporal lobe is what some have called the God spot. Stimulation here gives people intense feelings of joy and the sense of being close to some greater power or being "one with the universe." Some epileptic patients get these intense feelings just before seizures, and it is believed that some famous saints and other religious figures may have likewise suffered (if you can call it that!) from such 30 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  31. 31. Dr. C. George Boeree: General Psychology (1) disorders. The Parietal Lobe The furthest forward area of the parietal lobe, along the central gyrus nearest the frontal lobe, is the somatosensory area, which collects signals coming up from the body. Just behind that is the somatosensory association area, which further analyzes these bodily sensations. Specific areas specialize in locating and orienting us in three-dimensional space, and focusing on things in the outside world. The Occipital Lobe The occipital lobe is the smallest of the lobes and sits at the very back of the head. It has no clear borders and is differentiated primarily by function, i.e. vision. The various parts of the occipital lobe are labeled with a V followed by a number. The primary visual cortex at the very back of the occipital lobe is labeled V1, and receives input from the optic tract. It has a clear map of visual information that corresponds to the areas of the retina. The center of vision is greatly magnified. The individual neurons of V1 are extremely sensitive to very particular changes in input from the eyes. If there is a lesion somewhere in V1, there will be a "hole" in your vision called a scotoma. Oddly, some of the information from that "hole" seems to still be available, so that some people with scotomas can still react to stimuli there even though they don't consciously perceive them! This is called blindsight. V2 surrounds V1 and has many reciprocal connections with it. Much of its functioning is a repeat of V1's, but it detects more complex features, such as contours and the distinction between figure and ground. V3, just above V2, gets inputs from both V1 and V2. It appears to specialize in depth, distance, and global motion. V4 lies under V2. V4 is affected by attentional processes, and specializes in somewhat more complex perception of specific objects. V5 (also referred to as MT) is further forward in the occipital lobe, and processes complex motion. There seem to be two major pathways for visual information processing in the occipital lobe. There is a "where?" path, from V1 to V2 to V3 and V5, that interprets location and motion in space. And there is a "what?" path from V1 to V2 to V4 that determines the identity of an object. There are additional areas whose functions are not yet known. 31 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  32. 32. Dr. C. George Boeree: General Psychology (1) The Cingulate Gyrus The cingulate gyrus sits below the rest of the cerebral cortex, up against the corpus callosum and partially covering lower areas such as the basal ganglia, the limbic system, and the thalamus. Many people see it as the fifth lobe - others see it as part of the lobes above it, particularly the frontal lobe. It is so intimately connected with the limbic system that it is sometimes called the limbic gyrus. One of its major jobs is to keep your attention focused. When it isn't functioning properly, as seems to happen in schizophrenia, you are unable to distinguish real voices from imaginary ones. 32 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  33. 33. Dr. C. George Boeree: General Psychology (1) Methods 33 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  34. 34. Dr. C. George Boeree: General Psychology (1) Qualitative Methods Qualitative methods, as the name indicates, are methods that do not involve measurement or statistics. Because the natural sciences have had such resounding success with quantitative methods, qualitative methods are sometimes looked down upon as less scientific. That is, of course, a mistake. Qualitative methods have been in use in philosophy, sociology, and history for centuries, and many of the famous studies we refer to in psychology classes every day were actually qualitative! One qualitative method that goes back a long way is the case study. When physicians like Sigmund Freud became interested in psychological problems, they continued their tradition of writing and publishing descriptions of their most interesting patients, the treatments they attempted to use, and the progress of the disorder. Much of the content of abnormal psychology, for example, is built upon these case studies. Another example is the méthode clinique or clinical method. This method was particularly well used by Jean Piaget and his followers. The basic idea is to present a person (in Piaget’s case, usually a young child) with a situation or problem for them to deal with. The researcher observes how they handle the situation and asks them questions to try to understand the thought processes they are using. Another version of the méthode clinique is called experimental phenomenology. One study, for example, asked chess masters and novices to think out loud while playing chess, and analyzed the differences in approach. One more example is the method of introspection used by Wilhelm Wundt – often considered the founder of scientific psychology – and his students. Researchers paid careful attention to their own perceptions of simple events like colors, and noted changes in their perceptions following changes in the events. Probably the oldest qualitative method is naturalistic observation. This has been used by biologists who study animals in the wild (ethologists) for centuries, and by sociologists studying people’s behavior for nearly as long. The idea of naturalistic observation is to step back from the situation and make every effort not to interfere. A biologist studying birds, for example, may construct a blind – a small hut covered with natural materials – so as not to disturb the birds. Child psychologists often observe children in a similar way. In experimental schools, the children are often so used to being observed that the researchers don’t even have to hide! Recently, video and audio technology has allowed us to do the same with people. Unfortunately, the ethics of spying on people is very questionable! A variation on naturalistic observation used by some sociologists and psychologists is called participant observation. A sociologist who is interested in studying the lifestyles of people in some subculture (say a motorcycle gang) may actually join the subculture and interact with the people. Many anthropologists use this technique as well. In most cases, it is clear to all that the researcher is not really a part of the group, but sometimes the researcher hides his identity as a researcher. One of the most useful qualitative techniques is interviewing. It is often a part of all of the preceding methods. Contrary to what many people believe, interviewing is not easy. In fact, it is a rare person who is truly skillful at interviewing. You have to be very careful not to listen to the person you interview through any prejudiced ideas you might have. You have to make sure you are not leading the person in the direction you would like them to go. You have to make sure you don’t misinterpret what they say. In other words, you need to be very aware of your own biases! Many researchers using qualitative methods adhere to a school of thought called phenomenology, and refer to their methods as phenomenological methods. Phenomenology is the study of the contents of 34 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  35. 35. Dr. C. George Boeree: General Psychology (1) consciousness – phenomena – and phenomenological methods are ways of describing and analyzing these contents. Originally, the methods focussed on describing one’s own thought, feelings, and perceptions. For example, researchers would investigate their own experiences of an emotion such as anger, or cognitive processes like making a decision. As you can imagine, the problem of biases are even more difficult to handle in these kind of studies. Many people, if asked about their experiences of anger, might say something like "I could feel the adrenaline flowing through my veins!” Unfortunately, that is a prejudicial statement based on people’s common knowledge about the presence of adrenaline. In fact, nobody actually feels adrenaline in their veins! We may feel muscle tension, or the hair raising in our necks, or a change in our hearing – but not adrenaline in our veins. As time went on, other ways of investigating phenomena were added. For example, the researcher might ask other people to write what are called protocols – naïve descriptions of their experiences – and use them for analysis. This is done, for example, when the researcher wants to investigate something he or she doesn’t have personal experience with, such as a schizophrenics verbal hallucinations. There are arguments for and against the use of qualitative methods. The most common criticisms of qualitative methods revolve around the problem of bias mentioned above: It is much easier for biases to creep into qualitative studies than into quantitative ones. The great advantage of measurement is that, once we have agreed upon what constitutes a measure (say, a meter stick), everyone can use it and be fairly confident that what they measure is what anyone else would measure. If, on the other hand, we say "this looks like navy blue to me,” someone else might say "no, I think it’s purple,” and another person "no, it’s clearly royal blue!” The arguments for qualitative methods revolve around realism. Measures do not encompass the whole of an event. You can ask people to rate their anxiety, but how much will that tell you about what they are actually feeling? How do you measure something like love or hate? Or think about the anthropologist looking at a culture: Does counting the number of artifacts or timing rituals tell you much about their meaning to the people involved? Or consider a person’s personality: Do scores on personality tests tell you much about a person’s life or experiences? Qualitative researchers would say not much! Although quantitative methods are still preferred in psychology, more and more people are acknowledging that qualitative methods also have an important place. Not everything about human beings can be understood by measurement, or in laboratories, or by using rats and pigeons. 35 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  36. 36. Dr. C. George Boeree: General Psychology (1) Descriptive statistics Descriptive statistics are ways of summarizing large sets of quantitative (numerical) information. If you have a large number of measurements, the best thing you can do is to make a graph with all the possible scores along the bottom (x axis), and the number of times you came across that score recorded vertically (y axis) in the form of a bar. But such a graph is just plain hard to do statistical analyses with, so we have other, more numerical ways of summarizing the data. Here is a small set of data: The grades for 15 students. For our purposes, they range from 0 (failing) to 4 (an A), and go up in steps of .2. John 3.0 Mary 2.8 George 2.8 Beth 2.4 Sam 3.2 Judy 2.8 Fritz 1.8 Kate 3.8 Dave 2.6 Jenny 3.4 Mike 2.4 Sue 4.0 Don 3.4 Ellen 3.2 Orville 2.2 Here is the information in bar graph form: Central tendency Central tendency refers to the idea that there is one number that best summarizes the entire set of measurements, a number that is in some way "central" to the set. The mode. The mode is the measurement that has the greatest frequency, the one you found the most of. Although it isn't used that much, it is useful when differences are rare or when the differences are non numerical. The prototypical example of something is usually the mode. The mode for our example is 3.2. It is the grade with the most people (3). The median. The median is the number at which half your measurements are more than that number and 36 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  37. 37. Dr. C. George Boeree: General Psychology (1) half are less than that number. The median is actually a better measure of centrality than the mean if your data are skewed, meaning lopsided. If, for example, you have a dozen ordinary folks and one millionaire, the distribution of their wealth would be lopsided towards the ordinary people, and the millionaire would be an outlier, or highly deviant member of the group. The millionaire would influence the mean a great deal, making it seem like all the members of the group are doing quite well. The median would actually be closer to the mean of all the people other than the millionaire. The median for our example is 3.0. Half the people scored lower, and half higher (and one exactly). The mean. The mean is just the average. It is the sum of all your measurements, divided by the number of measurements. This is the most used measure of central tendency, because of its mathematical qualities. It works best if the data is distributed very evenly across the range, or is distributed in the form of a normal or bell-shaped curve (see below). One interesting thing about the mean is that it represents the expected value if the distribution of measurements were random! The mean or average for our example is 2.95. Statistical dispersion Dispersion refers to the idea that there is a second number which tells us how "spread out" all the measurements are from that central number. The range. The range is the measure from the smallest measurement to the largest one. This is the simplest measure of statistical dispersion or "spread." The range for our example is 2.2, the distance from the lowest score, 1.8, to the highest, 4.0. Interquartile range. A slightly more sophisticated measure is the interquartile range. If you divide the data into quartiles, meaning that one fourth of the measurements are in quartile 1, one fourth in 2, one fourth in 3, and one fourth in 4, you will get a number that divides 1 and 2 and a number that divides 3 and 4. You then measure the distance between those two numbers, which therefore contains half of the data. Notice that the number between quartile 2 and 3 is the median! The interquartile range for example is .9, because the quartiles divide roughly at 2.45 and 3.35. The reason for the odd dividing lines is because there are 15 pieces of data, which, of course, cannot be neatly divided into quartiles! The standard deviation. The standard deviation is the "average" degree to which scores deviate from the mean. More precisely, you measure how far all your measurements are from the mean, square each one, and add them all up. The result is called the variance. Take the square root of the variance, and you have the standard deviation. Like the mean, it is the "expected value" of how far the scores deviate from the mean. The standard deviation for our example is The normal curve At its simplest, the central tendency and the measure of dispersion describe a rectangle that is a summary of the set of data. On a more sophisticated level, these measures describe a curve, such as the normal curve, that contains the data most efficiently. This curve, also called the bell-shaped curve, represents a distribution that reflects certain probabilistic 37 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  38. 38. Dr. C. George Boeree: General Psychology (1) events when extended to an infinite number of measurements. It is an idealized version of what happens in many large sets of measurements: Most measurements fall in the middle, and fewer fall at points farther away from the middle. A simple example is height: Very few people are below 3 feet tall; very few are over 8 feet tall; most of us are somewhere between 5 and 6. The same applies to weight, IQ, and salaries! In the normal curve, the mean, median, and mode are all the same. One standard deviation below the mean contains 34.1% of the measures, as does one standard deviation above the mean. From one to two below contains 13.6%, as does from one to two above. From two to three standard deviations contains 2.1% on each end. An other way to look at it: Between one standard deviation below and above, we have 68% of the data; from two below to two above, we have 95%; from three below to three above, we have 99.7% Because of its mathematical properties, especially its close ties to probability theory, the normal curve is often used in statistics, with the assumption that the mean and standard deviation of a set of measurements define the distribution. Hopefully, it is obvious that this is not at all true. The best representation of your measurements is a diagram which includes all the measurements, not just their mean and standard deviation! Our example above is a clear example. A good real life example is IQ and intelligence: IQ tests are intentionally scored in such a way that they generate a normal curve, and because IQ tests are what we use to measure intelligence, we often assume that intelligence is normally distributed, which is not at all necessarily true! 38 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  39. 39. Dr. C. George Boeree: General Psychology (1) Correlation Correlation is what you are doing when you compare two sets of measurements (each set is called a variable). If you were to measure everyone’s height and weight, you could then compare heights and weights and see if they have any relationship to each other – any "co-relation," if you will. Of course, the taller you are, generally speaking, the more you weight. But it is obviously not a perfect co-relation, because some people are thin and some are fat. A perfect correlation is +1. Very close to perfect would be a comparison of men's shoe size and their... foot length. For example, here is some data: Shoe size John Dave Sam Jim Ed Bob Ted Matt Damian Horton 4 1/2 5 5 6 1/2 6 1/2 7 8 11 1/2 12 14 Foot length (inches) 9 1/4 9 3/8 9 1/4 9 1/2 9 3/4 9 3/4 10 1/8 11 11 1/4 11 3/8 We can arrange the data on a chart like this: This is called a scatter plot. The line is the line that describes the "best fit" – in other words, it accounts for the data most nicely. This one is not perfect – apparently, some guys buy shoes that are too tight, and some buy shoes that are too loose! But you can see by comparing the dots to the line, it's pretty close to a +1 correlation. 39 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  40. 40. Dr. C. George Boeree: General Psychology (1) Perfect correlation can also be -1. An example would be your car's fuel efficiency and how much money you need to spend for gas per so many miles. It should look like this: Most things have a correlation of 0 (or close to it). An example would be your shoe size vs your... SAT score. For a more real life example of data, along with a scatter plot and an actual correlation, is this one, which compares homicide rates with hand gun ownership. (The figures are real for the late 1980's.) Country USA Northern Ireland Finland Canada Australia Scotland Belgium Switzerland Norway France West Germany Spain The Netherlands England and Wales Homicide rate (per 100,000 per year) 8.8 5.2 2.9 2.1 2.0 1.8 1.8 1.2 1.2 1.2 1.2 1.0 0.9 0.7 Hand gun ownership (% of population) 29.0 1.5 7.0 4.0 2.0 0.5 6.0 14.0 3.5 5.5 6.5 2.0 1.0 0.5 40 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  41. 41. Dr. C. George Boeree: General Psychology (1) Here's the scatter plot: And the correlation: +.70. That is quite impressive, and maybe it says something about the various societies. If you are wondering about Switzerland's figures, it should be noted that every adult male is trained in the army and is required to maintain weapons in his home – just in case they get invaded by, say, Italy. On the other hand, you can see that Northern Ireland has a high homicide rate even though few people own guns. I think you can guess why! If you would like a more meaningful number than correlation itself, you can square it. This will give you a number that tells you how much of the variance (variation) in one or the other of the variables is "explained" by the other. So, for example, the .70 correlation above tells us that 49% of the variation in homicide rates is related to the ownership of hand guns. That leaves us with 51% of the variation we still need to account for. In psychology, we are generally impressed by correlations of .3 and higher. .8 or .9 blows us away. But one thing correlation cannot tell you is causality. Your grades and your SATs correlate pretty well – but which causes which? Even the homicide-hand gun example doesn't give you causation. Odds are always that there is something else that causes (or partially causes) two things to correlate. Perhaps coming from richer parents leads to both good grades and high SATs. Maybe a violent culture leads to both more guns and more violence. It takes other kinds of research – most especially experiments – to pin down cause and effect! 41 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  42. 42. Dr. C. George Boeree: General Psychology (1) Experiments A simple experiment starts out very much like correlation: You have two sets of measurements and you look to see if there is a relationship between them. You want to know if they "co-relate." The two sets of measures are called variables. Whatever it is, it has to vary in order for us to be interested in measuring it! The big difference between experiments and correlations is that, in experiments, you actually manipulate one of the variables. If you are manipulating one of the variables, that means that the second variable, if it "co-relates," was caused to do so by the variable you manipulated! You can tell what the causal effects of the first variable are on the second one – something you can never be quite sure of with a regular correlational study. The two variables have specific names: the one you manipulate is called the independent variable. Think of it like a radio knob: You can turn the knob because it is, to a degree, independent of the rest of the radio – it turns! The other variable is called the dependent variable. If the experiment shows that there is a relationship, then you know that it's this variable that depends on the first one – like the volume of your music depends on where you set the volume knob. If we measure the rotation of the knob (let's say somewhere between 0 and 10) and we set on each of the 10 settings, and then measure the loudness (in decibels, perhaps), we would find (probably) a close to perfect correlation. We use different kinds of statistics with experiments, but the idea is still the same, only this time we can conclude with considerable certainly that the setting of the knob causes the volume to change. Duh. But now let's consider a more interesting experiment: We want to test a new drug to see if it improves people's ability to remember things. Perhaps this drug might prove useful for helping Alzheimer's patients. We have two variables: the drug and memory. Each needs to be measured in some way. One common approach is to measure the independent variable in an all or none fashion: "0" would mean no pill; "1" would mean taking a pill. In a case like this, we usually call the "0" group the control group. The "1" group is called the experimental group or the treatment group. Very simple. (Sometimes, we let nature do the manipulation for us. For example, nature has made some people male and some people female. We are male or female long before we participate in some experiment, so we can comfortably say that it will be our maleness or femaleness that caused the results to some degree. This is called a subject variable. We often include subject variables such as male/female in our experiments because they are free and easy, and give us just a little more information.) The other variable in our memory pill experiment is a bit trickier: Perhaps we will need to develop some kind of memory test. Let's say we quickly show people 10 items, and then ask them to see how many of them they can remember. They can then get a score between 0 (nothing remembered) and 10 (all remembered). Now we are set: We can give half the people a pill and half not, then test them all on memory. Then we can see if there is a "co-relation." If the pill works, then those getting the pill will score high on the test, those who didn't will score less, and we will know why: the pill! 42 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  43. 43. Dr. C. George Boeree: General Psychology (1) Now of course things are a lot more complicated than this. First of all, we probably have to determine exactly how strong the pills are to be, how often they are to be taken, how long they need to be taken before we do our memory test, and so on. We also have to be very careful about all kinds of biases that might creep into the experiment. First, we are going to want to be sure that we will be able to generalize to the whole population. If we chose very specific, special people for our experiment, then our results might only apply to them, and not to all the other people that might benefit from the drug. So we need to have a random sample. This means that we should try, as best as we can, to pick our subjects (the people in the experiment) randomly from the target population. In this case, we might want to find a variety of Alzheimer patients from all over the country. If that's not possible, we should try at least to pick from a large group in a random fashion. Also, it would be a bad experiment if we allowed ourselves to pick some people to be in the control group and others in the experimental group on the basis of some quality they had. For example, if we gave the pill to 20 women and used 20 men as the control group, then we won't know if the pill helps everyone, or if there is something about men and women that makes them better or worse at memory (something that is actually a real issue!). So we have to have random assignment to conditions. All this randomization, and we should be set, right? Wrong. There is till experimenter bias and subject bias to throw things off. Subject bias happens when the people in your experiment have some kind of clue of what's going on and what is expected. A person who knows that the pill they are taking is supposed to improve their memory may try harder to remember, for example. On thing to do is to keep the subjects in the dark. Don't tell them what the pill is all about. Don't tell them what the memory test is all about. There can be an ethical problem here, and we often try to overcome that by asking the volunteers to sign a waiver and debriefing them afterwards, telling them how we fooled them. We also will want to give the people in the "0" condition some kind of pill, so that everyone is at least taking something, and no one knows who is and who is not getting the real pill. Fake pills are called placebos, and we often extend that term to cover all kinds of fake control conditions. If we want to know the effects of watching a violent movie, for example, we might have the control group watch a romantic comedy, so they are at least doing the same kind of activity. There is also experimenter bias, and this can be even more damaging than subject bias! You know how you want your study to come out, no matter how cool and objective you pretend to be. You may be giving subtle hints to your subjects, unintentionally. For example, you might give the people who took the pill just a tiny fraction more time to answer than you give the others. The only way to control this is to make sure that you are in the dark, too. Arrange things to make sure that you (and any assistants you may have) don't know which people took the real pill and which took the placebo, for example. When we combine both approaches, we call the experiment a double-blind: Both subjects and experimenters were "blind" to the conditions. Nowadays, anything but a double-blind experiment is treated with suspicion! Unfortunately, most experiments concerning therapy or educational techniques cannot be double-blind, so many important studies are not as strong as we would like them to be. In our example, the statistics we use will look at the differences in the scores of the control group and the 43 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  44. 44. Dr. C. George Boeree: General Psychology (1) experimental group. Each group will have it's mean (average) as well as a standard deviation (how spread out the test scores are). The statistics will determine whether or not the differences between the two group are likely to be significant or more likely to be the results of chance. Other studies might use statistics very similar to correlation. If, for example, we measure memory in 20 Alzheimer's patients before we start them on our new pill, and then give them another test after they've been on the pill for a month, then we can compare the two measurements as if we had measured the length of their feet and their shoe size. There are dozens of variations of experiment design and of the statistics we can use, each with their own advantages and disadvantages. Psychology students are traditionally well trained in statistics and experimental design, and they sometimes go on to careers involving data gathering and testing for companies, organizations, or the government. And some go on to do experiments in psychology itself! 44 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  45. 45. Dr. C. George Boeree: General Psychology (1) Sensation and Perception 45 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  46. 46. Dr. C. George Boeree: General Psychology (1) The Senses Taste (or gustation) There are about 10,000 taste buds on the tongue, clustered in papillae (those bumps all over your tongue). The taste buds are clusters of neuron bodies that line tiny pits in the papillae, and look sort of like a microscopic bunch of bananas. Molecules from the food we eat get mixed with saliva and find their way into the little pits and onto the surfaces of the neurons. Like a key fitting into a lock, these molecules open up tiny pores on the cell membranes and begin the process of firing the neuron very much the same way as the neurotransmitters do between neurons. There are only four basic tastes – that is, only four particular molecules that one or another neuron responds too on the tongue: Bitter - alkaloids Sweet - sugars Salt - sodium chlorids Sour - acids There may also be a fifth taste: Umami or savoriness, which involves a sensitivity to glutamate (which you may remember as one of the neurotransmitters). You find it in aged cheese, tomatos, mushrooms, meat, and soy sauce. It is best known as monosodium glutamate, which is used to enhance the flavor of meat. We experience salty and sour because the salt and acid ions directly open ion channels in the sensory neurons. Sweet, bitter, and umami, on the other hand, bind to proteins that have receptor sites. Our ability to taste bitter may have evolved in order to protect us from food poisoning. Note also that the tongue is sensitive to touch (hence the idea of texture in food), and to temperature and, of course, pain. Jalapeño peppers, for example, have a certain taste in the ordinary sense, but also provide us with delightful (!) sensations of pain. You might find it useful to know that, if your mouth is burning from eating peppers, it helps to drink milk, because milk fats dissolve the active chemical (capsaicin) while water merely spreads it around. In addition, the tongue is sensitive to cold, which can be triggered not only by actual low temperatures, but by chemicals such as menthol. Recent research with mice shows that some mice also have taste buds that respond to fats. Apparently, it is a genetic trait, one that may help us to understood why some people are more attracted to fatty foods than others. There are people that cannot taste anything. This is technically known as ageusia. Fortunately, it is very rare. Perhaps the biggest part of taste for us is, oddly, smell... 46 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  47. 47. Dr. C. George Boeree: General Psychology (1) Smell (olfaction) Smell works much like taste: It is also a "lock and key” sense. This time, it is a matter of moist air being drawn over a piece of specialized mucous membrane about the size of a dime at the top of your nasal cavity. With smell, we seem to be responding to the presence of some combination of seven basic molecules: Floral Pepperminty Musky Pungent (like spices) Camphoraceous (like mothballs or muscle liniments) Ethereal (like dry-cleaning fluid) Putrid (like rotten eggs) These are the seven smells suggested by the researcher John Amoore in 1952, when he also outlined his "lock and key" theory of how smells work. But it is far from certain that these are the fundamental scents – some researchers believe there are many more. The chemical senses are extremely sensitive, and this goes especially for smell. It is believed to be thousands of times more sensitive than taste and actually accounts for as much as 80 or 90% of what we perceive as flavor. There are roughly 40 million smell receptor cells in humans. Dogs have us beat, paws down, with 100 million cells. But they don't even rate compared with rabbits, with one billion cells. Mammals tend to have a good sense of smell, especially carnivores and their prey (for very obvious reasons!) Primates, however, have a relatively poor sense of smell. On the other hand, cetaceans (whales and dolphins) have no sense of smell at all! A lack of the sense of smell in humans is called anosmia. There has been considerable debate over many years about the existence of a smell-like sense that can detect the presence of molecules called pheromones. Many animals clearly can smell the presence of a potential mate over great distances. Male silkworms can detect even a simgle molecule that indicates a female! (It is the antennae that serve as smell organs in insects.) People can certainly smell other people – but is there a special smell that doesn’t really have a particular odor, but rather leads us to feel, well, those special "I want you” feelings? I think not, but there are many who disagree with me. Touch (tactile) The skin actually has three types of sensation: Pressure, temperature, and pain. Pressure is a simple matter of mechanical distortion, the bending of the dendrites of a mechanoceptor. When bent, the stress cause the opening of channels, the exchange of ions, and, of course, the firing of the neuron. In some cases, the dendrites are embedded in capsules which, when compressed, stimulate the neuron. Plus different neurons are sensitive to different kinds of pressure: light touch, firm pressure, and vibration. 47 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  48. 48. Dr. C. George Boeree: General Psychology (1) Temperature seems to be a very direct influence of the heat or cold opening certain ion gates. So far, we have found three of them: One for cold, one for hot, and one for very hot. Perhaps there are also ones for very cold and even just plain warm. It is interesting to note that menthol can also spark the cold receptors, and make us believe we are feeling cold when we are not! It is also peculiar that, when we touch a thermal grill – a surface that has alternating lines of cold and heat – we feel neither heat nor cold, but pain! I will talk about pain separately, but basically, pain is a matter of detecting certain chemicals indicative of tissue damage. With pain is classified itching and tickling. It is interesting that there is a chemical called capsaicin that acts on pain receptors just like "real” damage does. It is found in such things as jalapeño peppers, as mentioned above. Kinesthetic sense The kinesthetic sense is based on receptor neurons in the muscles and joints that basically work on the mechanical distortion principle. Some of these receptors are mechanoceptors just like those in the skin; others are spindles that begin to fire when stretched. Vestibular sense The vestibular sense tells you which way is up, how your body is oriented in relation to up, and how your body is moving in space. The sensations are based on hair cells - mechanoceptors with dendrites that resemble brushes. In the inner ear, there is a special arrangement of three semicircular canals around a central area. In the semicircular canals, the motion of the fluid as you spin causes gelatinous lumps called cupulas to bend one way or the other, which in turn causes the hair cells to bend. The three canals are oriented at roughly 90º to each other, and so give you spinning information in all three dimensions. 48 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  49. 49. Dr. C. George Boeree: General Psychology (1) The vestibular sense is also connected to parts of the brain that tell you when it is time to vomit. This is the cause of motion sickness. If you spin hard enough and then suddenly stop, the tiny current keeps going for a little bit, and gives you the sensation that you are still spinning, but in the opposite direction. Your brain may try to compensate for this, and cause you to fall or at very least feel dizzy. You can also confuse these canals when you take a shower and allow hot or cold water into your ear. The temperature changes can cause currents to develop that wind up feeling just like spinning, and you may get dizzy. The two central areas of this organ also have hair cells. The hair cells are embedded in gelatinous lumps called maculas which pulls them in one direction or another, depending on whether you are standing upright, bent over one way or another, or standing on your head. The bending of the hair cells again sends signals to the brain which interprets them accordingly. 49 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  50. 50. Dr. C. George Boeree: General Psychology (1) Hearing (audition) Hearing is also a matter of hair cells! You recall, I’m sure, the basic structure of the ear: The outer ear canal leads to the ear drum, a thin tissue stretched across the opening. Behind the ear drum, there is a sequence of three tiny bones that slightly amplify the vibrations of the ear drum. They end at another thin tissue that closes the true organ of hearing, called the cochlea. It is actually a tube, first bent in half, then wound up into a coil, and filled with fluid. Along this tube, there is a membrane that moves according to the wave patterns set up in the fluid. It has hair cells growing below it, and those hair cells send messages to the brain as to the wave patterns and changes they detect. That may sound complicated enough, but this description is actually highly simplified! Vision Vision is different from all the other senses. It involves receptor neurons that are sensitive to light. Light enters through the pupil and lens of the eye and is projected onto the back surface of the eye called the retina. The retina is composed of, among many other things, receptor neurons called rods and cones The rods are sensitive to a broad range of light, i.e. they tell us about "white.” They contain what is called visual purple (rhodopsin), a chemical that is sensitive to light. Note that a crucial part of this chemical is derived from vitamin A – so eat your carrots! The chemical breaks down when exposed to light and releases a protein (opsin) which eventually releases a neurotransmitter to send messages to the brain that "there is light.” Then the breakdown products are re-assembled back into rhodopsin. Cones are similar, but involve a chemical called iodopsin that is sensitive to more specific wavelengths of light, depending on pigments associated with the chemical. One kind of cone responds to red, one to green, and one to blue. Again, a protein (retinene) leads to the release of neurotransmitters, etc. Rods are far more sensitive than cones. This is why you see in "black and white” when there isn’t much light. Nocturnal animals tend to be color-blind, that is, they don’t have any cones, since color is of little use to them while high sensitivity is. Also, nocturnal animals usually have a shiny backing to their retina that reflects light back to the rods called a tapetum. It is usually made up of tiny crystals. This is why cats and other animals reflect light from their eyes! 50 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree
  51. 51. Dr. C. George Boeree: General Psychology (1) The great majority of color-blind people suffer from red-green color blindness. This comes about because they lack either red or green cones, so that red and green are indistinguishable. Everything is in shades of blue and yellow. It is much more common in men than women, occuring in about 1 in every 20 men. This is because the genes for red-green colorblindness are on the X chromosome of the 23rd pair. Since women have two X chromosomes, they must inherit the problem from both parents. On the other hand, a man with red-green colorblindness will not transmit the gene to his sons - only to his daughters (who will probably not be color blind!). Some people suffer from blue-yellow color blindness, which means that there is something wrong with their cones for blue. They see the world in shades of green and red. Since the gene for this kind of color blindness is on chromosome 7, it is equally distributed between men and women. It is, however, extremely rare. Also very rare is complete color blindness, which can mean that the person only has one kind of cone or none at all. As with all the senses, there is a great deal more to vision that this, but this will do for us. 51 | 107 © Copyright 2002 - 2006 Dr. C. George Boeree