1. Part 1: History and Overview
 human ancestors possessed basic human emotions, instincts, and behavioral drives
o most mammals have these things
o but they DON'T have language, which sets us apart from our ancestors more than
anything else
 humans can think about and directly communicate their feelings, whereas our ancestors could
only express their emotions through body-language
o this is good, because we can more easily categorize and understand our emotions
o this is also bad, because language, unlike body-language, is subjective; my
understanding of "happy" is not the same as someone else's
o as a result, it is hard to objectively study emotions
 today's lesson:
o animism
o mythology
o other things misattributed as causes of behavior
o subjective/inadequate data
 animism: attributing spirits to the behavior of humans and animals, possibly also plants, natural
forces, abstract concepts, and faraway things
o humans have "souls," and our souls control our bodies
o strange behavior comes from spiritual possession
 "spirited" "dispirited" "in good spirits" "drinking spirits"
o no scientific evidence for this
 feelings are sometimes falsely attributed to organs
o the heart doesn't actually have anything to do with love or sadness
o the stomach has nothing to do with bravery
 religion has made many statements about motivation and emotion, few of which can be backed
up by hard evidence
o religion is treated as an authority by many people, and those people don't always
question authority
 introspection: thinking about your own thoughts, how they come about, and what they mean
o many philosophers came up with ideas about emotion and motivation through
introspection
 Descartes invented dualism, the idea that the mind and body are two different entities
o your mind is your soul, your consciousness, and it controls the body
o the mind and the body cannot be reduced to the same thing
o the body is responsible for desire and motivation, but the mind is responsible for
emotion
o Descartes believed that the Pineal gland (the gland at the center of the brain) was the
interface between the mind and body
 this is partially right; the Pineal gland may be responsible for our mood
 Hobbes believed in hedonism, the idea that humans are inherently barbaric and simple
o all humans instinctively seek pleasure and avoid pain
o we cannot learn to betray our instincts; all human behavior is rooted to these desires
 Locke believed in the tabula rasa, the idea that the human mind starts off as a blank slate
o all thought and behavior comes from our experiences
~~~~~~~~~~~~

2.  today's lesson:
o the scientific method
o objective ways to study emotion and motivation
o discard preconceptions and build new ideas through systematic, empirical observation
 empiricism: using data from direct observation, not subjective experience
o introspection is not empirical, because you cannot objectively observe your own
emotions
o due to the limitations of language, you cannot explain your findings in a way other
people will understand completely
o if only there was some way to measure and explain your findings without room for
misinterpretation… hmm...
 operational definition: a definition that leaves no room for subjectivity or misinterpretation
o explains a concept in concrete, empirically measurable terms
 for example, an operational definition of anxiety might include sweating,
nausea, fast heartbeat, etc.
o scientists need operational definitions to replicate other scientists' experiments
 if you don't have an operational definition of the concept measured in another
scientist's experiment, how do you know you're both measuring the same
thing?
o at last, the problem of language is solved! scientists can now be objective about
emotion and motivation!
 operational definitions aren't enough; for true objectivity, you need to follow the scientific
method
o the scientific method relies on experiments that measure concepts with strict, easy-to-
understand operational definitions
o some scientists perform statistical analyses
o when the experiment is over, scientists attempt to publish their findings
o before the results can be published, they must undergo rigorous skeptical evaluation
from other scientists
 these scientists will point out flaws in your research
 they will also give you an idea of what to research next ("what DOESN'T this
study tell us?")
 NO UNQUESTIONED AUTHORITIES! if someone tells you you're wrong, you have
to take their opinions into consideration
o after the study gets published (IF it gets published), other scientists will replicate the
experiment
 if the new experiment gets similar results, your findings are correct! if not, your
findings may be discarded
 Thomas Kuhn came up with the idea of the paradigm shift: when someone discovers something
new (this could be a new technology, a new scientific principle, etc.), it triggers a revolution that
forces scientists to reconsider their worldview
o the video, "A Visual Metaphor for Paradigm Shifts," explains this concept in detail:
 the scientific world is a collection of facts
 scientists sometimes add new facts to this collection
 many scientific "facts" depend on the validity of certain theories, and these
theories exist within a paradigm
 if a scientific observation does not fit prevailing theories, scientists must edit or
discard those theories to account for the new observation

3.  if a new theory comes along that can explain the new observation, along with
every existing scientific fact, that theory goes on to shape a new paradigm in the
scientific world
 this is called a paradigm shift
o here's a real-world example of a paradigm shift
 Darwin explained evolution through a process called pangenesis
 lots of people accepted Darwin's explanation, because there were no
other theories at the time, nor was there any contradictory data
 but when Mendel did find contradictory data, he proposed the theory of
Mendelian inheritance, and Darwin's pangenesis was discarded
 Mendel, unlike Darwin, performed experiments before coming up with
theories
 it was Darwin who first suggested that we study emotions not through introspection, but
through empirical observation
o he believed we should study body language, because unlike our own emotions, body
language can be observed with objectivity
 when studying emotion and motivation from a genetic perspective, we should use these
methods:
o cross-species comparison: if multiple species react to a stimulus in the same way, those
species might be genetically related
o examination of expressions through development: if a certain behavior is present all
through an organism's development, that behavior might be innate and therefore
rooted in genes
o examination of expressions across human cultures: if people from all over the world
exhibit the same behavior, that behavior is probably universal; genes could be involved
o study of special populations: special populations are unaffected by the progression of
technology and society; if people from these populations exhibit a certain behavior, that
behavior could be innate
 James argued that we must abandon old philosophies and preconceptions, and instead use the
scientific method to study ourselves
o he believed that humans had a richer variety of emotions than any other animal
 Watson, like Locke, believed in the tabula rasa; he thought that all behaviors were learned
o "Give me a dozen healthy infants…" and I can raise them to do anything, regardless of
their race, gender, or cultural heritage
o he was a behaviorist
 Skinner was also a behaviorist; he believed that instinct was a myth
o he invented the Skinner box experiment
 put a small animal in a box with two buttons; one button drops a food pellet,
the other delivers an electric shock
 the animal will eventually learn to only push the food button, demonstrating a
learned behavior
 modern psychology, including the study of motivation and emotion, has been greatly influenced
by biology
o evolutionary biology helps psychologists understand why we exhibit certain behaviors
o physiology tells us where our behaviors come from (what part of the brain causes
happiness?)
o other modern influences: experimental psychology, biopsychology, evolutionary
psychology, animal behavior, neuroscience and neuroendocrinology

4.  the basic dimensions of motivation and emotion are best understood through natural selection
Part 2: The Evolution of Motivation and Emotion
 our three basic motivations:
o survival
o reproduction
o conflict
 motivations related to survival:
o thirst
 the feeling of "thirst" is regulated by our endocrine system
 when you get really thirsty, water is all you can think about
 when you get really, REALLY thirsty, you might become confused or start
hallucinating
 most people in North America never get this thirsty
o hunger
 hunger, like thirst, is regulated by our endocrine system
 and again, like thirst, most people in North America never get so hungry as to
consume their thoughts
o elimination
 unlike most animals, humans can have trouble with elimination
 we need to eliminate waste in specific places, like bathrooms; if we eliminate
anywhere else, it's embarrassing
 if you are physically unable to pass waste, it can be very distressing
o temperature regulation
 humans sweat when they get too hot; other animals have different methods of
regulating their temperature
 but no matter what we do to cool down or heat up, the drive itself is the same
o pain and escape behavior
 humans usually try to escape things that cause them pain (duh)
 painful things are generally bad for you; people who can't feel pain often hurt
themselves
o fear and avoidance
 as with pain, things that cause a fear response are usually bad for you
 however, there are lots of things we should be afraid of but aren't (cars, guns,
etc.); see evolutionary lag
 motivations related to reproduction
o (after all, what's the point of survival if you can't pass on your genes?)
o courtship
 you have to attract a mate before you can have sex with them
o sexual behavior
 if you don't have sex properly, you can't reproduce, and your genes don't get
passed down (again, duh)
o pregnancy, nursing, and nurturance of offspring
 some animals are driven to give birth under specific conditions; otherwise, their
offspring won't survive
 offspring may need parental guidance, depending on their species

5.  if human babies don’t have parents to look after them, they die
 nursing is also important; the benefits provided by milk are tremendous
o favoring kin
 by favoring kin, you improve your inclusive fitness (defined below)
 your kin shares your genes, so if you help them reproduce, you are effectively
passing down a portion of your genes
 motivations related to conflict
o threat and aggression
 if you threaten other members of your species, they will know not to mess with
you
 ...unless they're clearly stronger than you, in which case the "fear and
avoidance" motivation may take priority
o territoriality and dominance
 by securing territory, you also secure resources and a living space
 if you don't establish your place in the social hierarchy, other animals will mess
with your territory
 so basically: survive until you reproduce, reproduce successfully, and make sure your offspring
can survive until they reproduce, all while protecting your resources
 all of these motivations apply to humans, whether we are aware of them or not
o in 2013, Swami et al. conducted this study:
 recruited 120 male subjects
 placed the subjects in two conditions, 60 per condition
 the first condition consisted of hungry men
 the second condition consisted of men who had just finished eating
 sample populations: people who were about to enter/exit the cafeteria
 had subjects complete a survey to make sure they really were
hungry/full
 showed subjects an array of 3D models
 the models looked like blonde women wearing bikinis
 the only difference between each model was breast size; some models
had big breasts, others had smaller breasts
 experimenters used 3D models instead of real women, because real
women have physical differences besides breast size, and those
differences are hard to account for
 asked subjects to rate the models based on their attractiveness
 subjects in the hungry condition preferred big-breasted women
 why?
 big-breasted women have more body fat, and people high in body fat
tend to have better access to food
 if a man courts a big-breasted woman, he might get a meal out of it
 just to reiterate, this is not a conscious decision on the man's part
 so, yes, humans do possess subconscious motivations
 all motivations exist to help us pass down our genes
o individual selection: a gene that helps its owner survive is likely to get passed down
 survive to reproduce, reproduce to pass down genes, etc.
 a gene that doesn't help its owner survive is less likely to get passed down
 a gene that impedes its owner's survival is unlikely to get passed down, unless
that gene contributes to sexual selection (see below)

6. o kin selection: a gene that encourages you to help your kin is likely to get passed down,
because your kin shares your genes
 if your kin reproduce, some of your genes get passed down
 this may include the genes that encourage you to help your kin
 in this way, your genes are indirectly replicating themselves
 nepotism: the tendency to favor relatives over others, caused by kin selection
 to make things perfectly clear, kin selection produces nepotism; they
aren't the same thing
 how do you maximize both individual and kin selection?
o according to the principles of individual selection, if a gene impedes your survival, it
shouldn't get passed down
o ...unless your kin also have that gene, and it promotes nepotism
o so when does individual selection take precedence over kin selection?
 Hamilton's rule: if the cost of helping kin outweighs the reproductive benefits
of nepotism, the nepotism-promoting gene will not get passed down
 nepotism has to result in a net gain of reproductive fitness
 basically, r*B>C, where B=reproductive benefit, C=reproductive cost,
and r=coefficient of relatedness
 coefficient of relatedness: the degree to which you are genetically
related to your kin
 your parents have a CoR of .5, because you share half their
genes
 your uncle has a CoR of .25, because you share a quarter of his
genes
 identical twins have a CoR of 1, because they are perfect genetic
copies
 you are more likely to help your brother than your cousin, because your
brother has a higher CoR than your cousin
 this explains why some animals are willing to help children that aren't
their own
~~~~~~~~~~~~~~~~~~~~~
 humans make these decisions too (again, subconsciously)
o Madsen et al. conducted this experiment in 2007:
 had subjects stand in an uncomfortable squatting position
 for every 20 seconds they remained in that position, the experimenters gave
them money
 subjects were divided into several conditions based on who the money went to
 for one condition, subjects were told that they would receive the money
directly
 for another condition, subjects were told the money would be given to
their parents
 grandparents, cousins, best friends, a charity, etc.
 as CoR decreased, so too did the amount of time subjects were willing to remain
in the squatting position
 subjects held the position the longest when the money went directly to
them
 charity came in last place, followed closely by best friends
 conclusion: kin selection motivates human behavior

7.  recap of what fitness and inclusive fitness mean:
o fitness: reproductive success as measured by the number of offspring you have
o inclusive fitness: reproductive success as measured by the number of offspring you and
your kin have with respect to your kin’s CoR
 sexual selection: if a gene makes you more likely to secure a mate, it will probably get passed
down, even if it doesn't contribute to your survival
o sexual selection is often reflected in an animal's secondary sex characteristics (chest
hair, deep voice, etc.)
o some traits are selected even when they make survival more difficult
o think of a peacock's tail feathers
 they slow the peacock down, making it more difficult to survive, but they still
help him attract peahens
o fighting between male seals is another example of sexual selection
 fighting takes a lot of calories, and it may lead to death, but male seals still fight,
because it helps them secure territory and mates
o the red-backed spider plucks a "song" on the female's web to secure its mate
 this talent is in no way related to survival
 the female red-backed spider tries to eat the male regardless of how good the
"song" was, so this is clearly a dangerous behavior
 sexual selection can lead to great divergence within a species
o for example, the bluegill sunfish practices cuckoldry
 female sunfish are attracted to big males with large territories (called parental
males)
 not all males are big enough to secure attractive territories, but they still find a
way to reproduce
 shortly after a female lays her eggs, these smaller males (the cuckolders) will
swoop in and fertilize them before the parental males can
 if a parental male thinks the cuckolder fertilized most of the eggs, he will
destroy the whole clutch
 but some of the parental males end up raising the cuckolder's offspring
 cuckolders don't usually fertilize as many eggs as the parental males, but their
behavior is still selected for
 a cuckolder doesn't have to be big to reproduce, so he can start
reproducing earlier
 if a female can't find a good enough parental male, she may choose a
mate who is likely to be cuckolded
 the females would rather produce skilled cuckolders than weak
parental males
 to recap:
o organisms bring their genes into future generations via...
 pre-reproductive self-preservation (AKA survival)
 successful reproduction
 helping kin survive and reproduce
o genes that support these things are usually passed down, sometimes indirectly (kin
selection)
o genes that don't support these things are usually eliminated
o each new generation receives the subset of genes from the previous generations that
succeed in these endeavors

8. o for the fish example, neither type of sunfish male can be eliminated from the
population, because both males have genes that allow for survival and reproduction
 other important concepts:
o cultural evolution: changes in the behavior of a species that occurs over generations but
isn't related to genetics
 cultural evolution can also occur within generations
 in complex species like humans, it is easy for a whole generation to change its
behavior without genetic evolution
 learning, imitation, and language all facilitate cultural evolution
o evolutionary lag: our culture and environment changes more quickly than our genes
 instinctive behaviors conflict with cultural norms
 the biggest example is our diets; our instincts tell us to eat as many calories as
possible, because we evolved in an environment where we could never be sure
of our next meal
 nowadays, we are surrounded by calories; this new environment
conflicts with our instincts
 hopefully we will evolve to eat high-calorie foods less often
 evolution of emotions
o emotions: a predisposed reaction to a certain event
 elicited by social and environmental experiences
 different emotions lead to different behavior
o nature vs nurture
 do we learn our emotions, or are they instinctive? before we can answer this
question, we have to answer these:
 are emotions culturally universal?
 Ekman et al. performed this study:
 took pictures of people from North America expressing
different emotions
 showed these pictures to people from other cultures
and asked them to identify the emotions therein
 no matter where the experimenters went, the natives
guessed right more than 60% of the time (usually
around 80% at least)
 most primary emotions (happiness, sadness, fear,
anger, etc.) are expressed the same way in every culture
 are they found in other species?
 yes; Tyler showed us several pictures of animals expressing
emotions
 at one point, he showed us an entire chart of simian facial
expressions
 are they present early in development?
 many emotions are evident in infancy (crying under distress,
smiling under care, etc.)
 preverbal children are very good at expressing themselves
through body language
 are they involuntary?
 have you ever willed yourself to be happy?
 have you ever chosen not to feel sad or angry?

9.  are they stereotyped? are they expressed the same way every time?
would you ever confuse a happy person for a sad person?
 it is rare for someone to look sad when they feel happy or vice
versa
 (by the way, all of these things are related to Darwin's methods for
studying the genetic basis of emotion)
 we answered "yes" to all of these questions, so emotions are more nature than
nurture
 that's not to say nurture plays no role in the development of emotions
 learning and experience tell us whether an emotional reaction is
appropriate or inappropriate
 but even though nurture changes the way we express and perceive
emotions, it cannot change emotions themselves
 you don't learn to feel emotion
Part 3: Genetics, Learning, and Development
 selective breeding, the process of breeding plants or animals based on a favorable trait, began
with agriculture
o you only plant the best crop from each season, and eventually you will have nothing but
amazing crops
o the crops will probably never be perfect, but they will improve from generation to
generation
o back when agriculture was first conceived, nobody thought about genetics; they just
wanted better crops
 nowadays, we can directly manipulate an organism's genes to our specifications
o we can genetically engineer rice with extra vitamin A to make up for nutritional
deficiencies within a population
o we can genetically engineer crops to resist powerful pesticides; this makes farming
much easier
 as an example, Monsanto gave their crops resistance to glyphosate
 farmers can now use as much glyphosate as they need to secure their crops…
 ...so, are humans consuming more glyphosate? does glyphosate hurt us?
 we need to consider the ethics and consequences of genetic manipulation
 when breeding animals, there are other things we need to consider
o the behavior of simple organisms is usually driven by instinct, as opposed to learning
and experience
 humans and other complex animals rely greatly on learning
 learning does not completely override natural instinct, but it plays a very big
part in determining our behavior
o because of this connection between behavior and genetics, you can easily breed
behaviors into certain animals
 dogs are a good example of animals bred for behavior
 some dogs are bred for their loyalty and docility
 other dogs are bred to be hunters and fighters
 a dog that has been bred to behave one way can be trained to behave
differently, but instinct can override training

10.  this is why you occasionally hear stories about pit-bulls
attacking people, even though they were raised as pets
 horses are also bred for docility and calmness
 cattle and sheep are bred to produce the same behaviors
 cats are trained to exhibit inoffensive behavior and enjoy human contact
 lab rats are bred to be unaggressive, comfortable around humans, and tolerant
of confined spaces
 types of instinctive behavior:
o reflex: an innate, involuntary stimulus response
 reflexes can be simple (knee-jerk) or complicated (a cat righting itself while
falling)
 if a reflex becomes very complex, it stops being a reflex, and starts being
something else: a fixed action pattern (defined later)
 reflexes found in adult humans:
 breathing
 blinking
 shivering in the cold
 pulling hands away from hot surfaces
 knee-jerk
 salivation
 jumping when startled by a loud noise or sudden movement
 (all of these reflexes help us survive)
 reflexes found only in human infants:
 suckling when the cheek is stroked
 Babinski reflex: fanning toes when the sole of the foot is touched
 if this reflex does not disappear within the first few years of life,
it could indicate a neurological disorder
 for adults, there should either be no response, or we should curl
our toes down
 Moro reflex: throwing out the arms when startled
 the child may be trying to grasp something, presumably their
mother
 Palmer grasp: grabbing any object placed in the baby's palm
 again, the child may be grasping for the mother
 kicking feet out when held just above the ground
 tonic neck reflex: if you tilt a baby's head to one side while they are
lying on their back, the baby will stick one arm out and bend the other
back
 keeps the baby from rolling accidentally
 (if any of these reflexes are present in older children, it could indicate
developmental problems)
o fixed action pattern (FAP): instinctive, coordinated behaviors too complex to be
considered reflexes
 the term "fixed action pattern" has recently come under criticism, because it
implies that the action is always rigidly stereotyped, which it isn’t
 modal action pattern is the preferred term
 examples of FAPs in less complex organisms:
 grooming

11.  nest-building
 a pregnant mouse will build a nest for its offspring even if it was
raised without a nest
 swimming
 hissing or growling when enraged
 traits that most FAPs have in common:
 stereotyped: FAPs happen the same way, no matter where, when, or in
whom they occur
 all cats groom themselves the same way
 independence from immediate external stimulation; not all FAPs
require stimuli
 many FAPs occur long after the stimulus was presented
 the FAP does not change with the environment; when the FAP
starts, it doesn't usually stop
 behaviors not classified as FAPs are directed by
external/environmental conditions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 spontaneous: the timing, duration, and intensity of an FAP are not
determined by external stimuli or environmental conditions
 if it's been a while since the last time an animal performed a
certain FAP, that FAP will probably happen soon, and when it
happens it will be very intense
 for example, when carbon dioxide builds up in a male
stickleback fish's nest, it fans out the CO2 with its fins
 if a male stickleback is forced to go a long time without fanning
the nest, it will start fanning again as soon as possible and with
gusto
 independence from individual learning; if it's a learned behavior, it's not an FAP
o the FAP is not affected by learning experiences or changes to the environment during
development
o remember the thing about pregnant mice and nest-building?
 the genetics of behavior:
o as stated earlier, we can breed animals to exhibit certain motivations and emotions
o studies in humans have shown that behavior can be inherited
o some animals exhibit simple behaviors that can be traced to a single gene
 Whitney performed this experiment in 1969:
 C57 mice rarely vocalize
 JK mice vocalize often
 Whitney bred C57 mice and JK mice together
 56% of the crossbred f1 generation vocalized, compared to 3% of the
C57 and 68% of the JK
 according to Mendelian inheritance, this is what you would expect to
happen if the behavior was influenced by a single dominant gene
 Van Abeelen performed this experiment in 1967:
 Waltzer mice are observed to dance
 two Waltzers will produce a litter consisting entirely of dancing mice
 when Waltzers are bred with the non-Waltzing f1 generation, it
produces no dancing mice

12.  when two f1's are bred, 25% of offspring can dance
 Mendelian ratios suggest a single recessive gene
 the aforementioned studies were really exciting at the time
o complex behaviors are usually influenced by multiple genes
 Lagerspetz conducted this study in 1964:
 male mice were selectively bred for or against aggression over seven
generations
 only the most/least aggressive males were allowed to breed
 by the end of the experiment, there was a big difference between the
aggressive mice and unaggressive mice
 shows that aggression is genetic
 DeFries performed this experiment in 1978:
 mice were selectively bred for or against the tendency to explore open
spaces over thirty generations
 by the end of the experiment, mice in the high-exploration condition
were much more explorative than the control group
 mice in the low-exploration condition would freeze up in open spaces
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Plomin conducted this study in 1994:
 he compared monozygotic and dizygotic twins on a number of different
traits
 if one of the twins had Alzheimer's, autism, major affective disorder, a
reading disability, or alcoholism, the other twin was more likely to also
have that condition if the twins were monozygotic
 twins were raised in the same environment, so it's hard to say whether
that affects the conditions
 learning and flexibility
o learning helps us adapt to a complex, changing environment
o with learning, we can adapt to changes in the environment within one lifetime
o the ability to learn is driven by genetics
o some instincts depend on the ability to learn
 for example, many animals are driven to explore their environments
 this drive would be useless and dangerous if not for learning
 animals explore because they want to learn where to find resources and
how to avoid predators; they would not receive these benefits if they
couldn't learn
 play is another behavior influenced by learning
 many species engage in rough-and-tumble play, which teaches them
how to fight or defend themselves against predators
 simple forms of learning:
o habituation: the longer you are exposed to a stimulus, the less you notice it
o sensitization: the longer you are exposed to a stimulus, the more noticeable it becomes;
you are made sensitive to the stimulus
 classical conditioning: an animal learns to associate one stimulus with another and behaves
accordingly when either stimulus is presented
o the most famous example of classical conditioning is Pavlov's dog
 every time Pavlov fed his dog, he rang a bell
 the dog learned to associate the bell with food

13.  eventually, all Pavlov had to do was ring the bell, and the dog would salivate as
though in the presence of food
o types of stimuli and behavioral responses:
 unconditional stimulus (US): the original stimulus (food)
 unconditional response (UR): the behavioral response to the US (salivation)
 conditional stimulus (CS): the stimulus that becomes associated with the
original stimulus (bell)
 conditional response (CR): when the animal learns to associate the CS with the
US, it exhibits the UR when exposed to the CS (salivation in response to the bell)
 the CR is usually the same as the UR, but not always
o the three steps of classical conditioning:
 before conditioning: the US produces the UR; the CS isn't even a factor
 during conditioning: the US is repeatedly paired with the CS
 after conditioning: eventually, the CS will produce the CR, usually the same as
the UR
o some types of conditioning are so powerful, they only take one trial to set in
 Garcia conditioned animals to associate food with sickness
 if you irradiate an animal, it gets sick
 Garcia irradiated animals shortly after feeding them a specific food
 from then on, the animals refused to eat the food; just seeing it made
them sick
 this only took one trial
o humans can be conditioned to elicit specific emotional responses when exposed to
stimuli
 traumatic, sexual, and gratifying stimuli are very easily paired with emotions
 war veterans often suffer from PTSD
 gunfire is a good example of one-trial conditioning in humans
 people who have been shot at learn to associate loud, sudden
noises with life-threatening situations
 if the person you're dating always wears the same perfume, you will
associate that perfume with that person and the feelings they elicit in
you
 even if you smell the perfume in a mall years after breaking up,
it can still trigger positive emotions
 instrumental (operant) conditioning: an animal learns to respond to a stimulus in a certain way,
because that response is somehow reinforced
o dimensions of instrumental conditioning:
 positive: a stimulus is presented following a response
 negative: a stimulus is withdrawn following a response
 reinforcement: the presentation or withdrawal of a stimulus causes the
behavior to increase in frequency
 punishment: the presentation or withdrawal of a stimulus causes the behavior
to decrease in frequency
o types of instrumental conditioning
 positive reinforcement (usually just called reinforcement): a stimulus is
presented, increasing the frequency of a behavior
 for example, a dog can be trained to sit on command if you give it a
treat every time it sits when you tell it

14.  negative reinforcement (escape): a stimulus is withdrawn, increasing the
frequency of a behavior
 for example, if you electrocute a mouse until it pulls a lever, the mouse
will learn to pull the lever every time it gets shocked
 positive punishment (usually just called punishment): a stimulus is presented,
decreasing the frequency of a behavior
 for example, if you spray a cat with water every time it scratches the
sofa, it will eventually learn to stop scratching
 negative punishment (omission): a stimulus is withdrawn, decreasing the
frequency of a behavior
 for example, if you take away a child's toy after he/she misbehaves, the
child will eventually learn to stop misbehaving
o basically, animals repeat behaviors that lead to positive outcomes and curb behaviors
that lead to negative outcomes
 extinction: if a conditioned behavior/response is no longer reinforced, that behavior will
eventually cease
o if you reinforce a behavior every time it is performed, extinction happens more quickly
o for example, if you reward a dog every time it sits on command, and then you suddenly
stop rewarding the dog, it will stop sitting on command
o but if you gradually decrease the frequency with which you reward the dog, it will never
stop sitting, even after you stop feeding it entirely
 the physiology of reinforcement:
o rewards that occur in nature (food, drink, sex, etc.) are associated with increased
dopamine activity in the nucleus accumbens
o other rewards (money, etc.) will trigger the same response in humans
 conditioning doesn't always override FAPs
o FAPs are so deeply instinctive that they can occur even after conditioning
 you can train a pit-bull not to be aggressive, but the pit-bull may instinctively
return to those behaviors
 for example, mice instinctively avoid bright lights, even when it is in their best
interest to run towards a light
 in one experiment, mice were electrocuted every time a light shone into
the cage
 the mice could avoid the shock by running to the other side of the cage
 but if a light shone over the opposite end of the cage, the mice would
not run towards it, even though they knew they would get shocked
 Breland and Breland conducted this study in 1961:
 they were hired to train an animal (either a pig or a racoon) to put a
coin in a piggy bank
 here's how they planned to do it:
 reward animals for picking the coin up
 ...then reward them for carrying the coin to the bank
 ...then reward them for dropping it in the bank
 unfortunately, they couldn't even get passed the first part of the plan
 racoons would just roll the coin in their hands; it's what they
instinctively do with food
 pigs would drop the coins and "root" into the ground, looking
for more

15.  no matter what Breland and Breland tried, they could not train the
animals to work with the coins
 two more concepts related to learning:
o vicarious learning: learning through imitation
 also called modeling and contagion
 the animal observes a behavior, repeats it, and in repeating learns to perform
the behavior
 caused by mirror neurons
 offspring learn from their parents through imitation
o incentives/disincentives: humans do not need to have a reward or punishment in front
of them to be conditioned; all we need is the promise or representation of a reward
 for example, humans seek out money, even though money isn't something we
need in itself
 ...but money represents the things we need, so we continue to seek it out
Part 4: General Physiological Perspective (with special thanks to
Stephanie Williams, Jamie Gallagher, and an anonymous
contributor!)
 the human nervous system can be split into two sections: the central nervous system (CNS) and
the peripheral nervous system (PNS)
o the CNS includes the brain and spinal cord
o the PNS includes everything else
o both divisions of the nervous system are important to motivation and emotion
 for example, the PNS regulates many of the physical effects of emotion
(sweating, heart rate, stomach dropping, etc.)
 the components of the CNS are explained in detail here:
o spinal cord
 for the most part, the spinal cord is just a tract through which the brain sends
and receives information
 it also processes certain simple reflexes
o hindbrain
 contains the medulla, pons, and cerebellum
 the medulla controls our cardiac and respiratory systems; it makes us breathe
and regulates our heart beat
 it also causes vomiting and determines the constriction of blood vessels
 the pons maintains a wide variety of functions, including chewing, swallowing,
saliva secretion, tear production, facial expressions, eye movement, and balance
 the cerebellum helps us coordinate complex movements
 none of these parts are too involved in motivation or emotion
o midbrain
 contains the tectum and tegmentum
 the tectum processes auditory and visual sensory information
 we aren't completely sure what the tegmentum does, but it is probably involved
in eye movements

16. o forebrain
 contains the thalamus, hypothalamus, pituitary glands, basal ganglia, limbic
system, cerebral cortex, and many other parts…
 the thalamus can be thought of as a switchboard that receives sensory data and
sends it to other parts of the brain
 also determines our sleep/waking cycles
 the collection of structures known as the limbic system is located on
either side of the thalamus and maintains a variety of functions related
to motivation and emotion
 The hypothalamus controls a variety of metabolic processes, such as hunger,
thirst, sleep, fear, anger, body temperature, and parental urges
 It synthesizes and secretes hormones that control the behavior of the
pituitary gland
 the pituitary gland secretes hormones that control several physiological
processes, the most notable of which are related to reproduction and physical
growth
 the hypothalamus and the pituitary gland are both part of the
endocrine system, which controls the body's supply of hormones
 the basal ganglia is heavily involved in the brain's "reward" system
 the cerebral cortex contains several lobes that process sensory information and
help us form associations between objects and concepts
 it also sends information between the thalamus and the basal ganglia
 these structures are important, but not all of them are needed to survive
o cerebellar agenesis: a condition where the cerebellum fails to develop, leaving a
person's brain without its primary means of coordinating movement
 in 2014, Yu, Jians, Sun, and Zhang wrote a case study about a woman with
cerebellar agenesis
 she is very clumsy, and she gets dizzy and nauseous easily, but other than that
she's okay
 right now, she is the only person we currently know of who lives a healthy,
normal-ish life without their cerebellum
 perhaps, due to the plasticity of the brain, other nearby parts took over the
cerebellum's function?
o of course, some parts of the brain are vital; without the brainstem, for example, you
would certainly die
 the structure of the brain reflects its evolution
o our brain is similar to that of other mammals in several ways
 we have many parts in common, all sharing the same function and structure,
although the parts themselves are organized differently
o there are a few noticeable differences between the human nervous system and the
systems of other mammals:
 first, other animals tend to rely more on their olfaction (sense of smell), and this
is reflected in their neuroanatomy
 our brains also differ in terms of size and complexity
 animals lack some of the parts we have and vice versa
 for example, while we have a cerebral cortex, sharks and frogs have a
neocortex
o our posture also tells us something about how our brains evolved

17.  the shape and angle of our brain and brainstem is suited to a bipedal lifestyle
 quadrupedal animals have straight brainstems to compliment the flatness of
their backs, whereas our brainstem is pointed downward
 some scientists argue that human posture provides more space for the brain to
grow; this is not yet proven
 we will spend a lot of time talking about these parts of the human nervous system:
o the limbic system
 as stated above, the limbic system is a collection of parts that work together to
influence our motivations and emotions
 some parts of the limbic system are more heavily involved in motivation and
emotion than others
 we will discuss the limbic system in greater detail later
o the hypothalamus
 the hypothalamus is located right above the pituitary gland
 again, as stated above, it secretes hormones that control the pituitary
gland's function
 peptide hormones play an especially big role here, but more on that
later
 the hypothalamus responds to several stimuli:
 light
 to be more specific, the hypothalamus changes its function
based on an organism's photoperiod
 photoperiod: the amount of time each day an organism is
exposed to light
 the longer the photoperiod, the greater the duration of activity
in the hypothalamus
 when the photoperiod is short, people often become sad or
depressed, which could mean that the hypothalamus plays a
role in seasonal affective disorder
 olfactory stimuli
 the hypothalamus is thought to respond to pheromones
(pheromones will be explained next lecture)
 steroid hormones (again, next lecture)
 neural information
 the CNS and the PNS both influence the hypothalamus
 the hypothalamus is innervated by several other brain regions
 input from the autonomic nervous system (more on that later)
 various peptide hormones (next lecture), along with other substances
found in the blood, but only if they can cross the blood brain barrier
o the autonomic nervous system (ANS) contributes to many of the physical sensations
associated with our emotions
 the ANS is a huge component of the PNS
 it innervates all major organs in the body, as well as several glands
o there are three major divisions of the ANS: the enteric nervous system (ENS), the
sympathetic nervous system (SNS), and the parasympathetic nervous system (PSNS)
 the ENS influences the gastrointestinal system; it's not very important to
motivation and emotion

18.  the SNS and PSNS both stem from the spinal cord, but they are involved in
different nervous processes despite innervating the same organs
 the SNS connects to the thoracic and lumbar nerves, while the PSNS
connects to the cervical and sacral nerves
 figure 4-6 in the textbook tells you where these nerves lead
 the SNS dictates our fight/flight responses, while the PSNS controls our
rest/digest functions
 to put it another way, the SNS generates and expunges energy, while
the PSNS conserves and collects energy
o here's a more detailed list of what the SNS does when active:
 increases heart rate, respiratory rate, and blood pressure
 inhibits digestion, reduces blood flow to the digestive tract and skin
 increases blood flow to the muscles and lungs
 dilates the pupils
 causes piloerection (goose bumps)
 can sometimes cause spontaneous urination and defecation in moments of
intense arousal
o here's a list of what the PSNS does when active:
 decreases heart rate, respiratory rate, and blood pressure
 promotes digestion by increasing blood flow to the digestive tract
 stimulates secretion of saliva
 regulates sleep and sexual behaviors
o the adrenal glands
 the adrenal glands should really be thought of as two pairs of glands, because
each gland contains two semi-glands: the adrenal medulla and the adrenal
cortex
 the adrenal medulla is the core of the adrenal gland; it secretes catecholamines
when the SNS activates
 the adrenal cortex surrounds the medulla; it secretes steroids in response to
chemical stimulation, especially adrenocorticotropic hormone (ACTH) from the
pituitary
 the cortex has three layers:
 the first layer (reticularis) produces androgens, like testosterone and
DHEA
 the second layer produces aldosterone, which regulates blood pressure
and kidney activity among other things
 the third layer produces cortisol, which causes stress in humans
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 hormone: a substance released into the bloodstream that communicates with receptors at
distant site(s)
o the life of a hormone:
 a cell secretes the hormone into the bloodstream
 the hormone travels through blood vessels until it finds its target cell
 the hormone interacts with the cell's receptors, thus changing, activating, or
inhibiting the target cell's function
 neurotransmitter: a substance released into the synapse when a presynaptic neuron fires
o neurotransmitters are picked up by receptors on the postsynaptic neuron's dendritic
membrane

19. o neurotransmitters either increase or decrease the chance that the postsynaptic neuron
will fire
 neuromodulator: similar to a neurotransmitter, except it affects multiple neurons in the brain at
once
o neurotransmitter activity happens on a neuron-to-neuron basis, while neuromodulator
activity occurs all over the brain
o Neuromodulators travel through pathways in the brain to affect several places at the
same time
o the cerebrospinal fluid and ventricular system help determine where neuromodulators
go and how they work
 pheromone: any substance excreted by one individual that affects another individual's behavior
o most people think of pheromones as relating to sex/mating, but they can affect
behavior in all sorts of ways
o pheromones from one species are only meant to work on that species
 there could be some inter-species pheromone effects, but it usually doesn't
happen
 a pheromone's effect on one species will probably be different from its effect on
another species
 there are four main classifications of hormones/neurotransmitters: steroid hormones, peptide
hormones, monoamine hormones/neurotransmitters, and acetylcholine (ACh)
o steroid hormones
 small, lipid-soluble molecules that travel all throughout the body
 The steroid hormones' lipid-solubility makes it easy for them to get
where they need to go, because most cells have lipid membranes
 derived from cholesterol
 very slow
 they are excreted slowly, they act slowly, and they leave the body
slowly
 steroids can spend hours, days, or even months in the body before they
leave
 if steroids were water-soluble, they would leave the body much more
quickly, because water-soluble chemicals dissolve quickly in urine
 they usually act on intracellular receptors (receptors inside the cell), though
certain steroids act on extracellular receptors instead ( receptors on the cell
membrane)
 examples of steroids and the organs that produce them:
 the gonads produce androgens (like testosterone), estrogens, and
progesterone
 the adrenal cortex acts as a source of androgens, estrogens,
mineralocorticoids, and glucocorticoids (like cortisol)
 technically speaking, the adrenal cortex can only produce
cortisol, but it uses that cortisol to synthesize other hormones
 cortisol has 21 carbons; every time you remove a carbon, it
becomes a different hormone
 for example, testosterone has 19 carbons, so for the
adrenal cortex to make testosterone, all it has to do is
take 2 carbons away from cortisol

20.  but if the adrenal cortex can only produce cortisol, how do we know if
it's really producing all those other steroid hormones? how do we know
they aren't coming from somewhere else?
 because even after you take away all other possible sources of
those steroid hormones, they are still present in the body
 for example, a female mouse will still produce steroid
hormones after her ovaries have been removed
 so how do we know the adrenal cortex can only produce cortisol? after
all, those other hormones are clearly found in the adrenal cortex…
 we know because of experiments performed on something
called aromatase
 aromatase is an enzyme that uses androgens to synthesize
estrogens
 if you inject an aromatase inhibitor into the adrenal cortex, it
no longer produces estrogens
 this shows that all estrogens in the adrenal cortex are
synthesized from androgens; it doesn't produce its own
o peptide hormones
 chains of amino acids derived from proteins
 very fast-acting
 within seconds or minutes, they leave the body
 amino acid chains are easy to put together and break apart, so they are
secreted and absorbed very quickly
 peptide hormones are also water-soluble, which makes them even
easier to break down
 act on extracellular receptors
 peptide hormones are often too large to pass through the cell
membrane
 examples of peptide hormones and the organs that produce them:
 the pituitary gland is divided into two halves, each of which produces its
own set of hormones
 the anterior pituitary gland produces ACTH, beta endorphin,
LH, FSH, prolactin, and many more
 the posterior pituitary gland produces oxytocin and vasopressin
(ADH)
 the hypothalamus produces CRH, GnRH, and neuropeptide Y (NPY)
among others
 as stated in the previous lecture, the hypothalamus uses
hormones to act on the pituitary gland
 however, these hormones only act on the anterior pituitary, not
the posterior
 the hypothalamus does innervate the posterior
pituitary, but through nerve signals, not hormones
 of course, not all hormones produced by the hypothalamus are
used to manipulate the pituitary gland; which ones do?
 NPY
 pretty much anything with "releasing" in its name
 the gut produces cholecystokinin (CCK) and ghrelin

21.  the pancreas produces insulin and glucagon
 adipose produces leptin
 CCK, ghrelin, insulin, glucagon, and leptin will all be explained in
the next chapter
 the brain's ventricular system relays many hypothalamic and pituitary
hormones
 the limbic system, hypothalamus, and brainstem all contain peptide
hormones
o monoamine hormones and neurotransmitters
 like peptide hormones, but derived from single amino acids, rather than long
chains
 this makes them much smaller than peptide hormones
 still fast acting, still excreted quickly, still water-soluble, still act on extracellular
receptors
 examples:
 the adrenal medulla produces catecholamines like epinephrine and
norepinephrine (also called adrenaline and noradrenaline)
 epinephrine and norepinephrine are also used as
neurotransmitters
 the pineal gland produces indoleamines, like melatonin
 melatonin regulates your sleep cycle
 the more melatonin enters your system, the sleepier
you become
 when it's dark out, the pineal gland secretes more melatonin;
when it's bright out, not so much
 so be careful not to expose yourself to too much light in the
evening, or it could affect your circadian rhythm
 this is why pharmaceutical companies sell melatonin
supplements: for people who need to re-adjust their sleep-
cycles due to jet lag or staying up too late
 monoamine neurotransmitters are also derived from single amino acids
 glutamate, GABA, histamine, and glycine are all examples of monoamine
neurotransmitters
 there are two broad categories of monoamine neurotransmitters, both of which
are derived from different amino acids:
 catecholamines are synthesized from tyrosine
 tyrosine is synthesized into dopamine, which can then be
synthesized into norepinephrine, and then epinephrine
 as stated earlier, the adrenal medulla also produces the
catecholamines adrenaline and noradrenaline (same structure
as norepinephrine and epinephrine), but these are used as
hormones, not neurotransmitters
 indoleamines are synthesized from tryptophan
 tryptophan is synthesized into serotonin, which can then be
synthesized into melatonin
 the pineal gland also produces melatonin, but there it is used as
a hormone
 both types of monoamine transmitters have their own sets of neural pathways

22.  catecholamines have dopaminergic and noradrenergic pathways
 dopaminergic pathways:
 dopamine cell bodies are concentrated in two areas: the
substantia nigra and the ventral tegmental area
 both of these parts are in the brainstem
 axons from cell bodies in the substantia nigra ascend through
the medial forebrain bundle (MFB) to the striatum, an
important part of the limbic system
 axons from cell bodies in the ventral tegmental area also ascend
through the MFB; they end up in either the nucleus accumbens
(where dopamine is used to control reward mechanisms) or the
forebrain
 dopamine also performs certain actions in the posterior
pituitary, but not the anterior pituitary
 noradrenergic pathways:
 noradrenaline cell bodies are concentrated in the locus
coeruleus of the brainstem
 axons from these cell bodies ascend through the MFB into the
neocortex, then disperse throughout the limbic system, as well
as the cerebellum, spinal cord, and cortex
 this is called the neocortex circuit
 indoleamines have serotonergic pathways
 serotonergic pathways:
 serotonin cell bodies are concentrated in the raphe nuclei
 their axons ascend through the MFB into one of these
destinations: the thalamus, basal ganglia, limbic system, or
neocortex
 axons that enter the neocortex travel through the same circuit
as noradrenaline, taking them to the cerebellum, spinal cord,
and cortex
 a special note on serotonin:
 serotonin affects both the central and peripheral nervous
systems, but serotonin from the CNS does not mix with
serotonin from the PNS
 this is why antidepressants, specifically SSRI's (selective
serotonin reuptake inhibitors), only affect serotonin in the
synapses, not the brain
 just to make things perfectly clear, the synapses are
part of the PNS and the brain is part of the CNS, so
serotonin from either shouldn't mix
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 but you can't synthesize monoamine hormones and neurotransmitters without monoamines!
how do all those amino acids get to the brain in the first place?
o with help from the large neutral amino acid transporter
o tryptophan, tyrosine, phenylalanine, methionine, and branch-chained amino acids are
all carried by the large neutral amino acid transporter
 without it, none of these amino acids would make it past the blood-brain barrier
 this is usually the brain's only source of amino acids

23. o the amino acids listed above "compete" for access to the transporter
 if one amino acid gets disproportionate access, it causes a shortage of all the
others
 for example, too much phenylalanine could cause a shortage of tryptophan,
which would then lead to serotonin deficiency
 tryptophan and phenylalanine are both metabolized from food
 tryptophan is obtained from foods like chocolate and red wine, both of
which are highly sought-after
 of course, high levels of tryptophan lead to high levels of serotonin, so
chocolate and red wine are very rewarding foods
 conversely, serotonin levels plummet after eating food without
tryptophan
 phenylalanine is found in aspartame, a popular artificial sweetener, and
is much easier to metabolize than tryptophan
 so if you have too much soda, it could drastically affect your serotonin
levels
 acetylcholine (ACh)
o ACh is an important neurotransmitter in the autonomic nervous system and certain
parts of the brain
o it travels through both the sympathetic and parasympathetic nervous systems
 in the PSNS, ACh travels all the way from the spinal cord's preganglionic neurons
to the body's postganglionic neurons
 …but in the SNS, ACh only travels through the preganglionic neurons; the
postganglionic neurons receive norepinephrine instead
 why? because otherwise, the postganglionic neurons couldn't tell the difference
between signals from the SNS and PSNS
 if both the SNS and PSNS used ACh, the body would get confused
 but since the SNS switches to norepinephrine, postganglionic neurons can tell
which signals come from which system
Part 5: Hunger, Thirst, and Elimination
 As you can imagine, thirst is a pretty big motivator
o If you are adequately hydrated, you don't even think about being thirsty
o But as stated in a previous lecture, if you get really thirsty, it becomes all you can think
about
o Thirst is important for maintaining homeostasis
 if you drink too little water, your body motivates you to drink more by making
you thirsty
 drinking too much water can also have consequences, especially if you don't
have enough electrolytes; your blood becomes diluted, and your neurons have
trouble firing
o there are two types of water deficiencies:
 extracellular thirst: your body does not have enough extracellular fluid
 extracellular fluid is any fluid located outside of the body's cells
 found in blood vessels, cerebrospinal fluid, body cavities, etc.
 accounts for 1/3 of the total water in the body

24.  extracellular thirst is induced by perspiration, blood loss, diarrhea, and
heavy menstruation, all of which remove extracellular fluid
 extracellular thirst causes the volume of your blood to decrease, which
in turn decreases blood pressure
 here's how extracellular thirst works:
 it starts with a drop in blood volume
 as your blood pressure goes down, the baroreceptors in your
kidneys, which respond to changes in blood pressure, are
activated
 the kidneys start to produce an enzyme called renin
 renin synthesizes angiotensin, a peptide hormone that causes
vasoconstriction (the closing of the blood vessels)
 this boosts your blood pressure artificially, but it doesn't
really solve the problem
 renin gets its angiotensin from a chemical called
angiotensinogen, whose only purpose is to be
converted into angiotensin (hence the name) when
blood pressure drops
 there are four kinds of angiotensin, but angiotensin 2 -
the one we're talking about - is the only one you really
need to remember
 angiotensin 1, which helps control the amount
of angiotensin 2, is also somewhat important
 angiotensin also acts on the adrenal cortex to produce
aldosterone, which causes the kidneys to reabsorb sodium
 it acts on the pituitary as well, producing vasopressin (also
known as antidiuretic hormone), which causes the kidneys to
reabsorb water
 but wait! angiotensin is a peptide hormone! how could possibly it act on
the hypothalamus and pituitary, when peptide hormones are too large
to cross the blood-brain barrier?
 the subfornical organ, a part of the brain which lacks a blood-
brain barrier, reacts to angiotensin
 neurons in the subfornical organ project into the hypothalamus,
which then influences the pituitary
 the hypothalamus causes the sensation of thirst
 the subfornical organ also contains osmoreceptors, which
detect changes in the body's osmotic pressure
 cellular thirst: your body does not have enough intracellular fluid
 intracellular fluid is any fluid located inside the body's cells
 accounts for 2/3 of the total water in the body
 cellular thirst is induced by excess salt consumption
 cellular thirst also comes about when someone loses so much
extracellular fluid through perspiration or blood loss, the body's osmotic
pressure pulls water out of cells
 most of the thirst we experience is caused by excess salt
consumption

25.  but both salt consumption and severe fluid loss lead to an
increase in extracellular sodium
 here's how it works:
 excess sodium creates osmotic pressure that pulls water out of
the body's cells
 basically, water moves from an area of high
concentration (inside the cells) to an area of relatively
low concentration (outside the cells, where there is too
much salt to be counterbalanced by extracellular fluids)
 given the nature of the lipid bilayer, it's much easier to
pull water out of the cells than it is to pull sodium into
the cells
 osmoreceptors around the hypothalamus near the third
ventricle detect this change in osmotic pressure
 the osmoreceptors sample the fluid balance of the
blood and cerebrospinal fluid
 the hypothalamus stimulates thirst
 osmoreceptors are the brain's only way of knowing whether the body's
cells are thirsty
 if you inject a rodent with distilled water near its
osmoreceptors, the rodent will show signs of water-
overconsumption; it will refuse to drink, even when its cells are
actually thirsty
 the reverse is also true: if you inject saline near osmoreceptors,
the rodent starts drinking like crazy
o a few more concepts related to thirst:
 prandial drinking: drinking water because you feel thirsty immediately after
eating food
 when you're eating, you naturally want to drink at the same time
 the body is not yet overloaded with sodium, so there shouldn't be any
reason to drink…
 …but since the body will need to drink water eventually, it might as well
get started now
 prandial drinking may be a learned behavior; it is more convenient to
sip water during a meal than to gorge on water afterwards
 cessation of drinking: people only drink enough water to replenish their fluids;
no more
 it isn't often that someone accidentally drinks too much water
 the thing is, by the time we stop drinking, our fluid balance still hasn't
technically been restored; how do we know when to stop?
 as with prandial drinking, cessation could be anticipatory
 cessation is also thought to be derived from receptors in the mouth,
esophagus, and stomach, as well as from the swallowing reflex
 hunger is another vital motivator
o satiety, the feeling of fullness, is also important; without satiety, we would eat ourselves
to death
o of course, plenty of people do eat themselves to death nowadays…

26.  we evolved in an environment where no one could be sure of their next meal,
so it was safe to overeat every now and then
 today, most people have no trouble finding calories and sodium, but we still
overeat
o hunger and satiety make up two metabolic phases: feeding and fasting
 The feeding phase (absorptive) occurs shortly after eating and is triggered by
the parasympathetic nervous system
 the pancreas releases insulin, which promotes the absorption of
glucose - the body's most accessible means of storing energy - into fat
tissue
 the body is trying to store excess glucose in the form of longer-lasting
glycogen and fatty acids
 The fasting phase (utilization) starts if you go a long time without a meal and is
triggered by the sympathetic nervous system
 the pancreas releases glucagon, which breaks glycogen into glucose
 the body isn't getting any glucose from food, so it has to liberate the
energy in its stores
 if you lose too much glycogen while fasting, your body will switch to
ketone bodies and eventually fatty acids as a source of energy
 when the body switches to fatty acids, your hunger may
temporarily subside
 the reason you feel hungry after waking up is because your body is in
the fasting phase
o stomach distension, stomach pangs, and "growling" are usually associated with strong
hunger
o when the stomach is full, however, your hunger will subside
 you can stimulate the feeling of satiety in a rodent by blowing up a balloon in its
stomach
 one of the more common surgeries for weight loss is to remove part of the
stomach and staple it shut, reducing hunger
o these two chemicals are strongly associated with hunger and satiety:
 ghrelin is associated with hunger
 it is secreted by the intestines, the pancreas, and the epithelial cells
lining the stomach
 empty stomachs secrete more ghrelin, which helps explain why filling
the stomach reduces hunger
 ghrelin levels rise in the blood while fasting
 cholecystokinin (CCK) is associated with satiety
 if you inject a rodent with CCK, it does not seek food
 the intestines secrete CCK when they are filled with food
 there are CCK receptors throughout our nervous system, the most
important of which are found directly on the hypothalamus and through
the vagus nerve
o other factors that influence appetite:
 glucostatic factors:
 intracellular glucose (glucose found inside of the cells) is very important
for controlling hunger

27.  when your cells run out of glucose, the pancreas secretes
glucagon, the stomach secretes ghrelin, and you become hungry
 conversely, when your blood is filled with glucose (called blood
glucose or blood sugar, different from intracellular glucose in
that it isn't currently being used by the body as a source of
energy), the pancreas secretes insulin, the intestines secrete
CCK, and you become sated (full)
 diabetes: a condition where, no matter how much glucose a
person has in their blood, the pancreas never releases insulin;
that, or the body doesn't respond to insulin properly
 diabetics remain hungry even when their blood glucose
levels are extremely high
 people with diabetes must take insulin shots to regulate
blood glucose and control their appetites
 if a diabetic builds up resistance to insulin, blood
glucose will remain high, and they will continue to feel
hungry
 for comparison, if you inject a healthy person
with insulin, blood glucose will drop, and they
will start to feel hungry (the body interprets a
lack of blood glucose as having not eaten in a
while)
 your brain prefers glucose to all other forms of energy
 when you start running out of glycogen, the brain sucks up as
much glucose as possible
 even after the rest of your body has resorted to ketone bodies
and fatty acids, the brain will still be running on glucose
 we aren't sure if there are glucose receptors in the brain, so how does
the brain measure blood glucose levels?
 the liver does have glucose receptors, and it is connected to the
brain by the vagus nerve
 the liver uses its glucose receptors to tell the pancreas what to
do
 if there's too much glucose in the liver's hepatic portal
vein, it tells the pancreas to release insulin
 to little glucose, and it tells the pancreas to release
glucagon
 lipostatic factors:
 the body contains fatty acids, and those fatty acids are sometimes used
for energy
 …but the body doesn't have any fatty acid receptors, so it can't keep
track of fatty acids
 for a while, scientists had no idea how the body controlled lipid intake
 now they know that leptin, a hormone secreted by adipose tissue, is
responsible
 adipose tissue stores fatty acids, so if you have a lot of leptin, you also
have a lot of fatty acids

28.  leptin reduces your appetite and increases your metabolism; without it,
your body would never make any attempt at burning off excess fat
 mice who can't produce leptin (called OB mice) get really obese,
hence the name
 if you give an OB mouse a shot of leptin, it will stop eating
 some pharmaceutical companies have tried to market leptin as a diet
pill with limited success
 leptin will only curb your appetite if you have a leptin-related
metabolic disorder
 if you give a regular mouse a shot of leptin, it will not stop
eating
 neuropeptide Y
 NPY is thought to cause food-seeking behavior
 it is less active when you are well-fed and more active when you
are hungry
 obesity in humans is linked to excessive NPY
 NPY neurons are found in arcuate nucleus of the hypothalamus, located
at the base of the third ventricle
 if you inject NPY into a rat's hypothalamus, they will eat
ravenously
 chronic stress and a high-fat, high-sugar diet both lead to excessive NPY
 (according to studies done in monkeys)
 genetics also play a role
 interactions between these chemicals:
 leptin inhibits the secretion of NPY in the arcuate nucleus of the
hypothalamus, decreasing food intake
 ghrelin encourages the secretion of NPY in the arcuate nucleus of the
hypothalamus, increasing food intake
 brain physiology:
 the ventromedial hypothalamus causes satiety
 if you electrically stimulate the ventromedial hypothalamus, it
causes aphagia (unwillingness to eat)
 if you lesion the ventromedial hypothalamus, it causes
hyperphagia (overeating)
 the lateral hypothalamus causes hunger
 if you electrically stimulate the lateral hypothalamus, it causes
hyperphagia
 if you lesion the lateral hypothalamus, it causes aphagia
o so, to summarize:
 before a meal…
 insulin is low (not enough blood glucose to stimulate insulin production
in the pancreas)
 glucagon is high (the body needs to break down glycogen for energy)
 ghrelin is high (secreted by an empty stomach)
 CCK is low (the intestines only secrete CCK after receiving food)
 blood glucose is low (blood glucose comes from food, after all)
 leptin is unknown (leptin is released by adipose tissue, the amount of
which cannot be predicted)

29.  NPY is high (ghrelin stimulates production of NPY)
 after a meal…
 insulin is high (lots of blood glucose, so the liver tells the pancreas to
produce insulin)
 glucagon is low (the body needs to store energy, so no need for a
chemical that synthesizes glucose)
 ghrelin is low (the stomach is full; it doesn't produce as much ghrelin)
 CCK is high (food is in the intestines, so they release CCK)
 blood glucose is high (lots of glucose was recently absorbed into the
blood by the intestines)
 leptin is still unknown (one meal won't substantially increase your
adipose tissue)
 NPY is low (no ghrelin, no NPY production)
o psychological fun facts
 the mere odour and sight of food can stimulate hunger
 there are also social influences on feeding behavior
 if other people are eating, you will probably start eating too
 Herman et al. conducted this study in 2003
 told subjects that they were going to taste different kinds of
cookies and rate them
 experimenters also told subjects to rate their hunger
 subjects were divided into two conditions
 the first condition just ate the cookies and made ratings
 the second condition got to see other peoples' ratings
first, including their hunger ratings
 if subjects in the second condition saw that other people rated
themselves as hungry, they too rated themselves as feeling
hunger
 if subjects saw that other people rated themselves as
not hungry, they also rated themselves as not hungry
 but no matter how hungry or not hungry subjects in the second
condition rated themselves, they always ate the same number
of cookies as the first condition
 subjects only adjusted their perception of their own hunger; the
actual desire to eat food didn't change
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 de Castro conducted this study in 1994
o recruited over 500 subjects
o told them to record what they eat, how much they eat, and who they eat with for 7 days
o found that when subjects ate alone, they ate a certain amount of food at a certain pace
o when subjects ate with family and romantic partners, they ate more food, and they ate
it more quickly
o when subjects ate with friends, they also ate more food, but they ate slower
o this study contradicts Herman et al.'s study, because subjects' food intake was
dependent on social influences, not just their own expression/perception of hunger
 humans have an innate appetite for certain kinds of food
o we like sweet foods (with glucose) and salty foods (with sodium)

30. o humans also have a preference for fatty foods, but there isn't enough evidence to call
this preference "innate"
o the preference for sweets is observed in many, many other species
 sweet foods are useful, because they give us easy-to-digest, easy-to-burn
energy with little metabolic cost
 the tongue can directly sense sweetness; shows how important sweet foods are
to our evolution
o saltiness is one of the few other tastes that the tongue can sense directly
 other animals like salt too
 herbivores will travel great distances to eat salt, because plants are not rich in
sodium
 if you deprive a rodent of salt, they will drink nothing but high-salinity solutions
that would normally be disgusting
 humans ingest way more sodium than they should
 Health Canada says we should ingest around 1,500 mg of salt
 we should never exceed 2,300 mg
 but most adults consume over 3,400 mg every day
 this is bad, because excess sodium consumption can lead to
hypertension, high blood pressure, and other life-threatening conditions
 in addition to preferring certain foods, humans can also learn to avoid foods that cause sickness
o this type of avoidance only takes one trial
 if a food makes you sick once, you will probably never want to eat it again
o even the smell of sickening foods can trigger nausea
 if a food is very odorous, you will avoid other odorous foods, even if the smells
themselves are different
o dietary neophobia: animals (and some humans) tend to avoid foods they have never
eaten before
 elimination is another vital motivation, but we won't talk about it much
o there are three types of elimination - urination, defecation, and vomiting - but we will
only discuss vomiting
 the area postrema, which can be found at the base of the brain, controls the
vomiting reflex
 other parts of the brain also control the vomiting reflex, but the area
postrema is special…
 it does not have a blood-brain barrier, so it can sample the blood
without putting other parts of the brain at risk
 the area postrema contains receptors which detect certain toxins
 if you eat something poisonous, the area postrema will detect the poison and
trigger your vomiting reflex
 the area postrema only causes vomiting from dietary toxins; it does has nothing
to do with vomiting out of disgust
o disgust is a primary emotion, stereotyped across cultures
 it is also stereotyped across age; emerges early in infancy, does not really
change as people grow up
 even across species, disgust is universally triggered by feces, death, and odors of
decay

31. Part 6: Pain, Fear, and Comfort
 thermoregulation, the process of regulating temperature, is one of our basic motivators
o animals seek comfort in reaction to extreme heat and cold
o the more excessively hot or cold you become, the more you seek comfort; eventually,
it's all you can think about
 temperature is sensed by cutaneous receptors (receptors in the skin), as well as temperature-
sensitive neurons in the hypothalamus
o both sources of information converge in the hypothalamus
o the posterior nucleus of the hypothalamus motivates us to conserve heat, while the
preoptic nucleus motivates us to avoid heat
 both interact with the anterior pituitary through hormone actions
 the anterior pituitary secretes hormones that affect the rest of the body
o the posterior nucleus secretes thyroid-releasing hormone and sends it to the pituitary
 the pituitary then secretes thyroid hormones
 increases sympathetic nervous system activation
 shivering, goose bumps (piloerection), narrowing of the blood vessels
(vasoconstriction, especially when cold is related blood loss)
o the preoptic nucleus inhibits thyroid hormone secretion
 prevents the hypothalamus from releasing thyroid-releasing hormone
 deactivates sympathetic nervous system
 sweating, panting, thirst, vasodilation (dilates the blood vessels, especially in
the outer-skin to facilitate heat-loss)
 there are also behavioral responses to excess heat and cold
o we search for comfortable places
o we wear warm clothes or breathable t-shirts
 pain is another huge motivator
o pain disincentivizes maladaptive or self-injurious behaviors
o if you didn't have pain, there would be no reason to avoid hurting yourself
o when rest and recovery are needed, pain keeps you from being active and exacerbating
your condition
o in some cases, it is actually better to be active while injured (for example, while being
attacked)
 if this is the case, the body temporarily inhibits pain, a phenomenon called
analgesia
 the physiology and pathways of pain:
o nociceptors: receptors for pain
 they are free nerve endings, which means they don't need a chemical to be
activated
 great at responding to thermal and mechanical stimuli
 there are two types:
 C fibers are not myelinated, which means they send signals slowly (slow,
dull, aching pain)
 A-delta fibres are myelinated, so they send signals quickly (sharp, fast,
prickling pain)

32.  both fibres synapse in the dorsal horn of the spinal cord before ascending to the
brain
 there are three major pathways to the brain: spinothalamic,
spinoreticular, and spinomesencephalic
 the spinothalamic path leads to the thalamus, where pain is integrated
with emotional responses and general consciousness (you become
aware of your pain)
 if you electrically stimulate this tract, it causes pain; if you lesion
this tract, it inhibits pain
 the sensation of pain is specific to this tract; if you stimulate or
lesion the dorsal horn or thalamus, it does not affect pain
 the spinoreticular path goes through the reticular system, where pain
stimulates general arousal (shock or alertness), before completing in the
thalamus
 the spinomesencephalic tract leads to the midbrain, which is involved in
pretty much every motivation and emotion, before going to the
amygdala
 interacts with the hypothalamus, potentially causing analgesia
 two types of chemicals are involved in analgesia
o endorphins, such as ACTH (which promotes cortisol production) and beta-endorphin,
are released by the pituitary during stress
o enkephalins are small peptides derived from a variety of materials; they are
concentrated in the periaqueductal gray (PAG) and the dorsal horn of the spinal cord
o both hormones bind to endorphin receptors
o endorphin receptors are concentrated the PAG and dorsal horn, where enkephalins are
produced
o endorphins, enkephalins, and opioids (like heroin and morphine) interact with these
receptors to produce analgesia
o endorphins bind to receptors in the PAG, sending signals through descending tracts
from the brain to the spinal cord, where pain messages are inhibited by inhibitory
interneurons
 the pathways that move up from the spinal cord to the brain are called
ascending tracts
 the inhibitory interneurons can act on either the ascending tracts or the C and
A-delta fibres themselves
 inhibitory interneurons release GABA, which prevents the firing of neurons
~~~~~~~~~~~~~~~~~~~~~~~~~~~
 the perception of pain is very subjective
o pain perception is not always proportional to injury
 a paper cut or stubbed toe may elicit a stronger response than a broken leg
o perception of pain is partially determined by the body's analgesia-to-pain ratio
 a stubbed toe isn't that painful, but there's little to no analgesia
o the visual analog scale is a scale of subjective pain perception from 1-10, based on facial
expressions
 it's useful, but it doesn't objectively measure pain
o different people can have very different experiences of pain, and the same person can
experience the same painful event differently depending on a variety of factors

33.  while pain is a response to actual damage in the body, fear is the anticipation that damage
might occur
o if we didn't fear pain or injury, we would get injured and die more often
o we are most afraid of ancestral dangers (snakes, predators, spiders, heights, etc.), even
though these dangers are no longer threatening to us
 the visual cliff experiment:
 position a baby on a solid surface, half of which is transparent glass
 if the baby walks near this glass, it thinks it's crawling along a cliff
 the baby will not crawl over the glass, even when beckoned by its
mother
 the more active and self-locomotive a baby is, the better its depth-
perception, the less likely it is to crawl across the glass
 shows that our fear of heights is partially innate
 cars, guns, and knives, however, are not often feared, even though they are
much more dangerous
 this is a good example of evolutionary lag
 although fear is constrained by innate processes, it can be conditioned, sometimes in one trial
o a single traumatic event can cause lifelong phobias and post-traumatic stress
 in one case study, a woman had a traumatic experience at the dentist's office;
from then, on merely sitting in a chair that resembled her dentist’s chair was
enough to trigger panic attacks
o a series of subtraumatic events can also lead to fear conditioning
 if a mailman is frequently attacked or barked at by dogs, they can be gradually
conditioned to fear them
o fear can also be socially transmitted
 if a young monkey observes an adult monkey behaving fearfully towards an
object, the young monkey will also be fearful
 fear responses themselves are mostly innate
o learning new responses to fearful stimuli is difficult, sometimes impossible
o innate responses may interfere with learning new fear responses
 when rats receive inescapable electric shocks, they develop a fear response
(usually freezing or running away)
 it takes quite some time to train these rats to avoid the shock by pressing a lever
beforehand
o examples of innate responses:
 species-specific defense reactions:
 fleeing
 fighting
 freezing
 other reactions
 hiding
 burying, burrowing themselves or fearful objects
 perspiration
 spontaneous urination or defecation
 vocalizations, like crying and screaming
o it is very hard to learn not to do these things
~~~~~~~~~~~~~
 fear responses are triggered by the sympathetic nervous system

34. o unlike the PSNS, whose ganglia are located close to the organ tissues they affect, the
SNS's ganglia are chained together
o when one ganglion in the sympathetic chain ganglia fires, it propagates to every other
ganglion in the chain, thus affecting every organ in the SNS
 when something scares you, you need to kick every part of your body into high
gear at once
 parasympathetic functions do not demand whole-body reactions, so the PSNS
doesn't need a chain of close-together ganglia
o the SNS triggers these fear responses by way of noradrenaline:
 pupil dilation
 allows you to take in more of your surroundings
 increases respiratory and heart rate
 prepares you to run away from danger
 also prepares you for a fight
 inhibits stomach and intestinal function, preventing digestion
 the blood that normally goes to the stomach is directed instead to other
body parts, as described below
 inhibits production of saliva (but not salivary enzymes) in the salivary gland
 this dries the inside of your mouth, allowing you to take in more air
during a single breath
 inhibits the production of tears in the lacrimal glands
 decreases sexual response
 you don't want blood rushing into the wrong organs
 increases perspiration
 to cool you down while running/fighting
 liberates energy from stored fat and glucose
 fighting and fleeing both require a lot of energy
 prepares for defense reactions (fight/flight) in other ways
 increases blood pressure by constricting the blood vessels (vasoconstriction)
that supply the skin, digestive tract, brain, and smooth muscle
 by constricting blood vessels, the SNS directs blood away from these
parts of the body
 during fight/flight reactions, the skin, digestive tract, brain, and smooth
muscle do not need blood as much as the skeletal muscles
 speaking of which, the SNS also dilates the skeletal muscles' blood
vessels, giving them the oxygen, energy, and nutrients needed to carry
the body away from danger
 SNS vasoconstriction, like most other SNS functions is caused by
noradrenaline and adrenaline
 there are multiple adrenergic receptors throughout the body,
each of which respond to both noradrenaline and adrenaline
 most of the time, these receptors exhibit the same response to
adrenaline and noradrenaline
 there are two adrenergic receptors that control
vasoconstriction: alpha 1 adrenergic receptors, and beta 2
adrenergic receptors

35.  alpha 1 adrenergic receptors constrict blood vessels in
the skin, digestive tract, brain, and smooth muscle
when exposed to adrenaline or noradrenaline
 beta 2 adrenergic receptors dilate arteries in the
skeletal muscles when exposed to adrenaline or
noradrenaline
 increases function of the adrenal medulla, which produces catecholamines like
noradrenaline
 prolongs the fight/flight response
 if it weren't for the SNS's stimulation of the adrenal medulla, the
fight/flight reaction would end really quickly, because noradrenaline is a
monoamine neurotransmitter
o catecholamines in the central nervous system, like dopamine and norepinephrine, are
also elevated following exposure to aversive or fearful stimuli
 promotes general arousal and awareness
 the increase in dopamine levels does not necessarily indicate a reward
mechanism
o during extreme or intense fear, these reactions are observed:
 loss of peripheral vision
 piloerection (goose bumps)
 this has an evolutionary context
 when humans had fur, goose bumps raised their hackles, making them
seem larger and more imposing
 shaking
 caused by over-activation of the skeletal muscles
 spontaneous urination and defecation
 could disgust predators, making them less likely to eat us
o the amygdala is also part of the fear response
 like the hypothalamus, the amygdala is a complex organ containing many nuclei
 it tells us whether to approach or avoid stimuli by conditioning anger and fear
 electrical stimulation of the amygdala's lateral areas can induce fear, defensive
behaviors, and alertness
 electrical stimulation of other areas can diminish fear and defensive behaviors
 human fMRI studies have shown that the amygdala activates upon viewing
fearful facial expressions
 there are two amygdala nuclei to consider
 the basolateral nucleus integrates stimuli and sensory memories with
feelings of fear
 helps us learn to be afraid of things
 allows to recall whether stimuli should be avoided
 every kind of stimulus, from visual to olfactory, can be
conditioned with a fear response
 the cortical nucleus is responsible for our sense of smell and
pheromone processing
 it receives input from the olfactory bulb and olfactory cortex
 the centromedial nucleus is involved in the arousal of emotions
 the amygdala is connected to many other parts of the brain, including…

36.  the hypothalamus, which controls the SNS and therefore the fear
response
 the thalamic reticular nucleus, which integrates sensory input with
physical reflexes
 the trigeminal and facial nuclei, which processes facial expressions
 as stated earlier, the amygdala affects our perception of
emotional faces
 the ventral tegmental area, locus coeruleus, and laterodorsal
tegmental nucleus, each of which produce a specific catecholamine
 the ventral tegmental area contains dopamine cell bodies
 the locus coeruleus synthesizes norepinephrine
 the laterodorsal tegmental nucleus activates the production of
epinephrine
 Urbach-Weithe disease: a disease that gradually atrophies the amygdala
 people with this disease are generally less afraid of things
 they have no special memory for traumatic events
 they also have difficulty recognizing fear in others, which relates to the
amygdala's relationship with the trigeminal and facial nuclei
o pheromones may be involved in fear for certain species
 mice and cattle, for example, will avoid areas where other members of their
species have been afraid
 when studying pheromones of fear, you have to account for a variety of
confounding variables
 mice spontaneously defecate when afraid, so other mice may be
avoiding places out of disgust rather than fear
 humans are instinctively frightened by things that move slowly towards us
o even stimuli that wouldn't normally be fearful can cause a slight, general sense of
unease
Part 7: Reproduction (with special thanks to an
anonymous contributor)
 animals compete for all sorts of things (resources, territory, social status, etc.)
 all of these things help us survive and reproduce, but the act of reproduction itself drives
competition more than anything
 because males and females have different reproductive goals, they compete with each-other as
much as they compete with themselves
o in mammals, there are pretty clear differences between the sexes
 males…
 have a constant supply of sperm
 usually invest less in their offspring
 they do not have to carry children to term, nor do they always
nurture their young
 never become infertile
 may seek multiple mates

37.  compete for females
 females…
 have a select number of eggs, only one of which is available at a time
 generally invest more in offspring
 will eventually become infertile, assuming they live long enough
 usually only mate with one (or two) males
 allow males to compete for them
 in some species, females compete for males
o as stated earlier, these differences sometimes lead to competition between males and
females
 females have to be cautious and selective while mating, while males want to
mate with as many females as possible
 if a female mates in the wrong conditions (wrong season, wrong
location, wrong amount of food, etc.), it could hurt the offspring
 they usually want to mate with the best male they can find, to the
exclusion of other males
 what females define as the "best male" varies between species
 males cannot always be certain that their children are their own (the degree to
which a male is certain of his paternity is called paternity confidence)
 to prevent uncertainty of paternity, many males will guard their mates
from other males
 sometimes, if a male realizes he has been cuckolded, he will kill the
offspring to preserve resources and restart the female's reproductive
cycle
 key terms related to mating and bonding:
o K-selection: a species has a small amount of offspring and invests in them quite a bit
 results in higher offspring survivability
 maintains a constant population
 humans and humpback whales are both K-selectionists
o r-selection: a species has lots of offspring and doesn't invest much in any of them
 very brief juvenile period in these species
 low offspring survivability
 creates large population changes
 mice and fruit flies are both r-selectionists
o monogamy: one female and one male are paired together
 monogamy is good for less dominant males who have trouble controlling
resources and territory, because monogamy gives them a higher chance of
mating with at least one female
 the best males can only take one female, which leaves the other
females for less successful males
 leads to female-female competition for access to males (occurs in humans, bald
eagles, and some other mammals)
 serial monogamy: several brief monogamous partnerships in succession
 advantages of monogamous male-female bonding:
 there is less risk of catching diseases, because you only ever have sex
with one person
 biparental (two-parent) care increases offspring success and
survivability

38.  females also benefit; they receive assistance with raising kids, and they
are protected by male partners
 disadvantages of monogamous male-female bonding:
 excludes all other mating opportunities; what if someone better comes
along?
 worse, what if your partner is infertile?
 and what if your partner deceives you? what if they mate with someone
else on the side?
 this is especially threatening to males, who have a lot to lose
from cuckoldry
 males may abandon, neglect, or abuse the cuckolder male's
children, as well as the cuckolding female herself
o polygamy: males and females both engage in multiple pairings
 in polygamous societies, males compete more often than females, because
females are the choosier sex
 diseases are rampant due to frequent sexual activity, and paternity isn't always
certain
 males will not bond with or care for young, because the children might not be
theirs
 females take care of each-others' children to make up for male absence
o polygyny: males have multiple pairings with several females, sometimes in a harem
 polygynous societies reward dominant males at the exclusion of lower status
males
 male-male competition is very intense in these societies
 polygyny a good arrangement for lower-status females, who are usually
guaranteed access to high-status males
 there is some interfemale competition as to who gets the most resources from
their male
o polyandry: females have multiple pairings with several males
 hive insects often live in polyandrous societies
 polyandry is rare in mammalian species
 when polyandry occurs, it is usually motivated by kinship; two or more brothers
share a single wife
 low-status females lose out in this arrangement, because males only have to
choose the best females
 there is some intermale competition as to who gets to impregnate the female
first
o promiscuity: no exclusive romantic partnerships within a species
 this is true in animals like mice
 human reproductive strategies:
o we are a K-selected species
o biparental care is common but not universal; lots of single mothers and fathers
o serial monogamy is prevalent in western culture, but other cultures use other mating
strategies
 animals depend on certain stimuli to trigger mating behavior
o visual stimuli, tactile stimuli, and olfactory stimuli all play a role
o many species rely on visual stimuli, but the most obvious example is blood-engorged
genitalia, especially in female chimpanzees

39. o other species, like moths, respond to the olfactory stimulation of pheromones
o tactile (touch) stimuli are also important
 female mice will arch their backs in a way that makes it easier for males to
mount them; this behavior is seen in other species as well
 some snails pierce each-other with love darts (yes, that is the actual term)
during mating dances
 around the end of the dart, there is a mucous that contains hormones
which open the snails' copulatory orifices, increasing the chance of
mating success
 sexual behavior in males:
o mounting: climbing atop the female to begin sexual intercourse
o intromission: the act of inserting the penis into a vagina
o ejaculation: the ejection of semen from the penis
 sexual physiology in males:
o the SNS and the PSNS both play a role in sexual behavior
 the SNS is responsible for ejaculation, while the PSNS causes erections
 the SNS innervates the genitals from the lumbar nerves, while the PSNS
innervates genitals from the sacral nerves
o hormones are also a factor
 men go through a daily cycle of high-to-low testosterone levels
 testosterone levels peak at about 8 AM and decrease throughout the
day, only to spike back up the following morning
 sexually active men of all ages go through this cycle, but younger males
have higher levels of testosterone overall than do older males
 this cycle is dependent on hormone transmission within the hypothalamo-
pituitary-adrenal axis (HPA axis)
 the hypothalamus secretes gonadotropin releasing hormone (GnRH)…
 which causes the anterior pituitary to release follicle-stimulating
hormone (FSH) and luteinizing hormone (LH)…
 which cause the testicles to secrete testosterone…
 which sends negative feedback to the hypothalamus and pituitary,
telling them to stop producing hormones…
 and when testosterone levels get low enough, the cycle starts again
 daily variance of testosterone has no effect on sexual response in humans
 if you inject testosterone into a man, they will probably not become
more sexually active
 castration reduces male sexual response over time
 if a male animal frequently has sex, it will take longer to stop
performing sexual behaviors
 hormones from the adrenal glands can also affect post-castration sexual
behavior
 Phoenix performed this experiment in 1974:
 they castrated rhesus monkeys and injected them with
dihydrotestosterone (DHT)
 control group consisted of uncastrated rhesus monkeys
 over time, with help from DHT injections, sexual behavior
increased in the castrated monkeys
 "intact" monkeys were unaffected by the injections