Enables us to understand & make sense of the sensations we continually experience
Perception & sensation are dual processes; you need both!
Sequence of events that produce a sensation: 6. You respond! 5. Signal reaches the brain. 4. As a signal passes along sensory nerves to CNS, it is further coded. 3. Receptor sends out a coded electrochemical signal. 2. Stimulates a receptor cell in a sense organ (energy must be sufficient enough for receptor to respond). 1. Need a form of energy, either external or internal.
Highly specialized cells
Located in eyes, ears, nose, tongue, skin, & elsewhere
Accomplishes coded task
The Brain “Creates” Sensory Experiences:
The brain is isolated within the skull, listening to the “clicking” of coded neural signals coming over millions of nerve fibers.
The “clicks” of an optical nerve are not any more visual than the “clicks” of an auditory nerve, but the brain interprets the “clicks” on an optic nerve as visual nerve energy & they give rise to visual experience instead of sounds, tastes, or smells.
Sensation: The Process
Process by which physical properties of stimuli are converted into neural signals & then transmitted to brain
When deprived of sensations, we create it by means of hallucinations
What is the least amount of sensation we can detect?
What stimuli we can detect seems to be designed to maximize our survival.
`You have heard a sound. How much stronger does the sound have to be before you notice that it has become louder?`
Aka: “just noticeable difference”
Will vary from person to person
The stronger the stimulation, the bigger the difference must be in order for you to detect it
Some sense are more sensitive than others to change
Stimuli below threshold
Q: Can we sense or be affected by subthreshold stimuli that remain outside our conscious awareness?
Our sensitivity to an unchanging stimulus tends to decrease over time
Light enters the eye through the cornea
Light passes through the pupil
Light passes through the lens
Light leaving the lens is projected on the retina , in the back of the eyeball
2 Types of light-sensitive receptors:
1. Cones (named for their shape)
Located in the center of the retina
Responds to light & dark & colors
Operates chiefly in daylight
Connected to bipolar neurons
2. Rods (named for their shape)
Responds to only varying degrees of light & dark, not colors
Chiefly responsible for “night vision”
Connected to bipolar neurons
Neurons with only one axon & one dendrite
Carry info to ganglion cells optic nerve brain
Wavelength determines what we experience as color
As wavelength increases from small to large our sensations shift from violet-blue (short) to orange (med.) to red (long)
Functions of the Visual System:
Static visual acuity
Dynamic visual acuity
Rods & cones become more sensitive to light in response to lowered levels of illumination
Helmholtz suggested certain cones were sensitive to green, while others were sensitive to red, or blue & by mixing the three you could experience all hues
Opponent Processing Theory
Hering proposed the existence of 3 pairs of color recptors
Processing Visual Information
Research: feature detectors
Do we process visual information hierarchically?
Q: If a tree falls in the woods and there is no one there to hear it, does it make a sound? (How would psychologists answer this question)
Thousands of tiny hair cells
Fibers are pushed & pulled by vibrations of basilar membrane
Properties of Sound:
Pitch Perception (2 Views)
-sound is detected by different places that are vibrating on the basilar membrane
- sounds of different pitch cause different rates of neural firing
Skin – largest sensory organ
Different receptors for different sense?
Some have a high tolerance for pain
Beliefs about pain can affect our perception of it
Research has found that pain is not related to level of tissue damage
2 Types of pain
Quick & sharp
Dull & throbbing
Gate-Control Theory: a “neurological gate” in the spinal cord controls transmission of pain impulses to the brain
Current emotional state affects pain perception
Sense of smell is @ 10,000 x’s more sensitive than taste
Appears to decrease with age
How we smell:
Substance enters nasal passage
Dissolves in moist nasal tissue
Receptor cells in olfactory epithelium
Why can we smell alcohol in drinks and not sugar in drinks?
Related to gender & age
Can people distinguish many different odors?
4 Basic Tastes:
Why do we perceive more flavors?
Kinesthesia & Vestibular Sense
Gives information about the location of our body parts
Allows us to perform movements
Where does information come from?
Monitors equilibrium and gives information regarding body position, movement, and acceleration
2 Kinds of Vestibular Sensation:
Body Rotation – arises from 3 semicircular canals in inner ear.
Gravitation & Movement – forward, backward, up, and down.
Sense arises from vestibular sacs
The “way” in which we select & organize sensory input
How we experience meaningful patterns in the jumble of sensory information
Can we attend to all stimuli?
Advantages = we don’t get overwhelmed
Disadvantages = we “miss” stimuli that may be meaningful
Laws of Perceptual Grouping:(108)
Laws of Similarity
Law of Good Continuation
Law of Proximity
Law of Closure
Laws of Common Region
Laws of Simplicity
Tendency to perceive aspects of the world as unchanging despite varied sensory input
Size Constancy – tendency to perceive a physical object as having a constant size.
Shape Constancy – to perceive a physical object as having a constant shape.
Brightness Constancy – to perceive objects as having a constant brightness even when they are viewed under different illumination.
Figure & Ground Relationship:
Figure – has a definite shape & location in space.
Ground – has no shape, seems to continue behind the figure & has no definite location.