Sensation and Perception

1.6 and 2.1

sensation

the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment

transduction

conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brains can interpret.

absolute threshold

the minimum stimulation needed to detect a particular stimulus 50 percent of the time

just noticeable difference

difference in stimuli required to detect a difference between the stimuli

sensory adaptation

diminished sensitivity as a consequence of constant stimulation

weber’s law

the smallest change in a stimulus you can detect (the Just Noticeable Difference) is a constant proportion of the original stimulus's intensity, not a fixed amount

sensory interaction

the principle that one sense may influence another, as when the smell of food influences its taste

synesthesia

describing one kind of sensation in terms of another ("a loud color", "a sweet sound")

retina

the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information

blind spot

the point at which the optic nerve leaves the eye, creating a "blind" spot because no receptor cells are located there

visual/optic nerve

carries neural impulses from the eye to the brain

lens

Focuses light on the retina

accommodation

the process by which the eye's lens changes shape to focus near or far objects on the retina

nearsightedness

a condition in which nearby objects are seen more clearly than distant objects because distant objects focus in front of the retina

farsightedness

a condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind the retina

photoreceptors

rods and cones

rods

retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond

cones (blue, green, red)

retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations.

trichromatic theory

theory of color vision that proposes three types of cones: red, blue, and green

opponent process theory

the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green

afterimages

images that occur when a visual sensation persists for a brief time even after the original stimulus is removed, explained by the opponent process theory

ganglion cells

In the retina, the specialized neurons that connect to the bipolar cells; the bundled axons of the ganglion cells form the optic nerve.

dichromatism

A type of color blindness where one of the three basic color mechanisms is absent or not functioning.

monochromatism

only able to perceive one color

prosopagnosia

inability to recognize faces

blindsight

a condition in which a person can respond to a visual stimulus without consciously experiencing it

wavelength

the distance from the peak of one light or sound wave to the peak of the next. Determines hue or pitch

pitch

a tone's experienced highness or lowness; depends on frequency

amplitude

Height of a wave, brightness or volume

loudness

A sensory characteristic of sound produced by the amplitude (intensity) of the sound wave

pitch perception

The ability to distinguish between tones played at differing frequencies

place theory

in hearing, the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated

volley theory

a theory that proposes that our brain decodes pitch by noticing the frequency at which groups of hair cells on the basilar membrane are firing

frequency theory

in hearing, the theory that the speed of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch

sound localization

we can locate sounds based on which ear they strike first

conduction deafness

An inability to hear resulting from damage to structures of the middle or inner ear.

sensorineural deafness

deafness that results from damage to the auditory nerve

olfactory system

Gives us our sense of smell, which is the strongest of the five senses

pheromones

odorless chemicals that serve as social signals to members of one's species

gustation

sense of taste

Sweet, sour, salty, bitter, umami, oleogustus

The five basic tastes: sweet, sour, salty, bitter, umami, and fatty.

taste receptors

chemical receptors on the tongue that decode molecules of food or drink to identify them

supertasters

people with heightened sensitivity to all tastes and mouth sensations

medium tasters

average number of taste buds

nontasters

people who cannot detect bitter compounds except at very high concentrations

warm/cold receptors

Thermoreceptors detect temperature. Cold receptors are more numerous in the skin, and warm receptors are more numerous in deep tissue

gate control theory

the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass on to the brain

phantom limb

a continuing sensation of an amputated body part

vestibular sense

sense of balance

semicircular canals

three fluid-filled canals in the inner ear responsible for our sense of balance

kinethesis

the sense of movement and body position

bottom-up processing

the analysis of the smaller features to build up to a complete perception

top-down processing

a progression from the whole to the elements

schema

a conceptual framework a person uses to make sense of the world

perceptual set

a mental predisposition to perceive one thing and not another

gestalt psychology

a psychological approach that emphasizes that we often perceive the whole rather than the sum of the parts

closure

the tendency to complete figures that are incomplete

figure and ground

the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground)

proximity

(n.) nearness, closeness

similarity

the tendency to perceive things that look similar to each other as being part of the same group

attention

focusing awareness on a narrowed range of stimuli or events

selective attention

the ability to focus on only one stimulus from among all sensory input

cocktail part effect

Ability to concentrate on one voice amongst a crowd

inattentional blindness

failure to detect stimuli that are in plain sight when our attention is focused elsewhere

change blindness

failing to notice changes in the environment; a form of inattentional blindness

binocular depth cues

clues about distance based on the differing views of the two eyes, for example retinal disparity

retinal disparity

a binocular cue for perceiving depth by comparing images from the retinas in the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object.

convergence

A binocular cue for perceiving depth; the extent to which the eyes converge inward when looking at an object

monocular depth cues

cues of depth perception that are available to each eye alone

relative clarity

a monocular cue for perceiving depth; hazy objects are farther away than sharp, clear objects

relative size

a monocular cue for perceiving depth; the smaller retinal image is farther away

texture gradient

the tendency for textured surfaces to appear to become smaller and finer as distance from the viewer increases

linear perspective

A monocular cue for perceiving depth; the more parallel lines converge, the greater their perceived distance.

interposition

if one object partially blocks our view of another, we perceive it as closer

apparent movement

the perception that a stationary object is moving

visual perception constancies

Maintain the perception of an object even when the images of the object in the visual field change.