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