Chapter 3: Sensation and Perception

trichromatic theory

Thomas Young's (and sorta Hermann von Helmholtz) theory of color vision that proposes three types of cones: red, blue, and green. Different shades of color correspond to different amounts of light received by each of these three types of cones. The combination of the cones and the rate at which they are firing determines what color you see. When you mix red, blue, and green light you see white, which is the reflection of the entire visual spectrum.

blind spot

area in the retina where the axons of the three layers of retinal cells exit the eye to form the optic nerve, insensitive to light

olfactory bulbs

areas of the brain located just above the sinus cavity and just below the frontal lobes that receive information from the olfactory reeptor cells

retinal disparity

binocular cue in depth and distance perception. Each eye sees the world slightly differently, and the difference is greater for closer objects.

convergence

binocular: eyes get closer when you are looking at closer objects

auditory nerve

bundle of axons from the hair cells in the inner ear

conduction hearing impairment

caused by damage to eardrum or bones, usually by infection. Hearing aids help.

cornea

clear membrane on the surface of the eye that provides protection. It has a fixed curvature through which light bends. Lasers or other methods can be used to correct the curvature.

flavor

combination of taste and smell

hertz

cycles or waves per second, a measurement of frequency. There is a limited range of frequencies that people can hear. (20-20,000)

optical illusions

discrepancy between visual appearance and physical reality

sensory conflict theory

explanation for motion sickness that states that the conflicting sensory stimuli from vision and the fluid in one's ears confuses the brain and results in dizziness or nausea

reflex arc

fast response to pain where the signal doesn't go to the brain

sound shadow

head acts as a barrier to sound waves, so one ear usually hears something a tiny bit before the other and helps the person figure out where the sound is coming from

afterimages

images that occur when a visual sensation persists for a brief time after the original stimulus is removed

perceptual set

implies that people interpret the same visual stimulus differently depending on context (images of a man's face/yoga woman)

olfactory cilia

little hairs protruding off of olfactory receptor cells that transduce the signal to a neural impulse and send it the olfactory nerve and then the olfactory bulb

motion parallax

monocular cue: when you are moving, it seems like you are moving past closer objects much faster than objects that are further away—another way to perceive distance

accommodation

monocular cue: your eye takes a second to adjust to seeing something at a different distance

pictorial depth cues

monocular cues: linear perspective, texture gradient, interposition, relative size, height in plane, light and shadow

akinetopsia

motion blindness where a person sees movement as one would a multiple exposure photograph

gate-control theory of pain

nociceptive signals must pass through a "gate" at the spinal cord, but only so many can fit through

relative size

perception that occurs when objects that a person expects to be of a certain size appear to be small and are, therefore, assumed to be further away

nerve hearing impairment

problems in the inner, auditory pathways, or cortical areas of the brain. Normal aging causes some loss of hair cells. Hearing aids don't help, however cochlear implants can help with transduction.

Gestalt principles of grouping

proximity, similarity, continuity, closure, continguity

pitch

psychological experience of sound that corresponds to the frequency of the sound waves; higher frequencies are perceived as higher pitches

anhidrosis

rare condition in which an individual cannot feel pain, but can still be injured

olfaction

sensation of smell

skin senses

sensations of touch, pressure, temperature, and pain

kinesthetic sense

sense of the location of body parts in relation to the ground and each other

auditory canal

short tunnel that runs from the pinna to the eardrum

cochlea

snail-shaped structure of the inner ear that is filled with fluid

sensory adaptation

tendency of sensory receptor cells to become less responsive to an unchanging stimulus. Affects smell, touch, and taste (NOT sight, due to tiny movements of the eye called microsaccades or saccadic movements)

habituation

tendency of the brain to stop attending to constant, unchanging information. Sensory receptor cells are still responding to stimulation, but the information is not being relayed from the lower centers of the brain to the cortex.

depth perception

the ability to perceive the world in three dimensions through linear perspective, relative size, overlap of objects, aerial perspective, texture gradient, motion parallax, accommodation, convergence, and binocular disparity

somesthetic senses

the body senses consisting of the skin senses, the kinesthetic sense, and the vestibular senses

visual accommodation

the change in the thickness of the lens, which is located behind the iris, as the eye focuses on objects that are far away or close. Presbyopia occurs when the lens hardens and people can no longer focus on objects that are close to them

absolute threshold

the lowest level of stimulation that a person can consciously detect 50% of the time the stimulation is present

perception

the method by which the sensations experienced at any given moment are interpreted and organized in some meaningful fashion

color blindness

the more accurate term is color-deficient vision, which is a sex linked trait caused by defective cones in the retina. Three types: 1. Monochrome color blindness: black and white 2. Dichromatic vision: one cone does not work properly, usually resulting in red-green color deficiency (either protanopia or deuteranopia) and seeing mostly blue, yellow, and shades of gray OR rarely resulting in tritanopia which is blue-yellow color deficiency

transduction

the process of converting outside stimuli, such as light, into neural activity

sensation

the process that occurs when special receptors in the sense organs are activated, allowing various forms of outside stimuli to become neural signals in the brain

dark adaptation

the recovery of the eye's sensitivity to visual stimuli in darkness after exposure to bright lights. Gets slower with age.

light adaptation

the recovery of the eye's sensitivity to visual stimuli in light after exposure to darkness. Quicker than the opposite process.

vestibular sense

the sensations of movement, balance, and body position

gustation

the sense of taste

just noticeable difference (difference threshold)

the smallest difference between two stimuli that is detectable 50% of the time. Example: if there are 5 teaspoons of sugar in a cup of coffee, you need to add another entire teaspoon to be able to taste the difference at least half the time.

linear perspective

the tendency for parallel lines to appear to converge on each other; helps with distance perception (ex: lanes on a long highway look like they merge in the distance)

figure-ground

the tendency to perceive objects, or figures, as existing on a background

contiguity

the tendency to perceive two things that happen close together in time to be related

pinna

the visible part of the ear

opponent-process theory

theory of color vision that proposes visual neurons are stimulated by light of one color and inhibited by light of another color. Red and green are paired, and blue and yellow are paired (that's why there are no reddish-greens or bluish-yellow). This explains the coloring of afterimages-if you stare at something green for a long time, the cell receiving the stimulus is fatigued, and once you look away the responsiveness to green is lowered so you see red.

place theory

theory of pitch that states that different pitches are experienced by the stimulation of hair cells in different locations on the organ of Corti. This can occur at frequencies above 1000 Hz.

volley principle

theory of pitch that states that frequencies from about 400 Hz to 4000 Hz cause the hair cells (auditory neurons) to fire in a volley pattern, or take turns firing

frequency theory

theory of pitch that states that pith is related to the speed of vibrations in the basilar membrane. This assumes that all the neurons are firing at the same time, which can only occur at frequencies below 1000 Hz.

perceptual constancies

things about an object such as size, shape, hue, brightness, and location look different depending on where you are looking from, but that doesn't mean the object has changed

antinociceptive signals

things like endorphins, narcotics, cognitive-emotive techniques, and other stimulation that can block pain by "crowding" the gate

subliminal perception

unconscious awareness of stimuli that are not strong enough to reach an absolute threshold. Growing body of evidence about this, although it's still debated.

reversible figures

visual illusions in which the figure and round can be reversed

cones

visual sensory receptors found at the back of the retina, responsible for color vision and sharpness of vision

rods

visual sensory receptors found at the back of the retina, responsible for non-color sensitivity to low levels of light