AP Psychology Unit 3 - Sensation & Perception

absolute threshold

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

difference threshold or JND

The smallest difference between two stimuli that can be consistently detected on 50% of trials.

threshold

The minimum intensity of a stimulus necessary to evoke a response (e.g., auditory or excitatory).

amplitude

The maximum deviation of a wave from its median intensity; determines brightness in light and loudness in sound.

sensation

The process by which our sensory receptors and nervous system receive and represent stimulus energies.

sensory adaptation

Diminished sensitivity as a consequence of constant, prolonged, or repeated stimulation.

sensory interaction

The principle that one sense may influence another, such as smell influencing taste.

synesthesia

A condition in which stimulation of one sense generates a simultaneous sensation in another.

transduction

Conversion of one form of energy into another, such as transforming sights into neural impulses.

wavelength

The distance from the peak of one wave to the peak of the next; determines hue in light and pitch in sound.

Weber’s law

The principle that, to be perceived as different, two stimuli must differ by a constant percentage rather than a constant amount.

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fovea

A small depression in the central retina where cone cells are most concentrated and vision is clearest.

afterimage

The image that remains after a stimulus ends; usually complementary in color (e.g., yellow leads to a blue afterimage).

accommodation

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

blind spot

The point where the optic nerve leaves the eye, containing no receptor cells.

blindsight

The capacity to detect or localize visual stimuli in a "blind" portion of the visual field following cortical damage.

cones

Retinal receptor cells concentrated near the center of the retina that detect fine detail and color in well lit conditions.

Dichromats

Individuals with partial color blindness who contain only two types of cone photopigments.

Farsightedness

Hyperopia; a refractive error where the focal point lies behind the retina, blurring close objects.

Ganglion cells

The only neurons in the retina that send signals to the brain; their axons form the optic nerve.

lens

A transparent, biconvex structure behind the iris that provides adjustable focus for the eye.

monochromats

Individuals with partial color blindness containing only one type of cone photopigment; see only in shades of one color.

Nearsightedness

Myopia; a refractive error where the focal point lies in front of the retina, blurring distant objects.

opponent process theory

The theory that opposing retinal processes (red green, blue yellow, white black) enable color vision; explains afterimages.

optic nerve

The second cranial nerve that carries neural impulses from the eye to the brain.

Photoreceptors

Visual receptors in the retina, specifically rods and cones.

prosopagnosia

A condition where the ability to recognize faces is impaired, though other object recognition remains intact.

retina

The light sensitive inner surface of the eye containing rods, cones, and layers of neurons.

rods

Retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision.

trichromatic theory

The Young Helmholtz theory that the retina contains three color receptors (red, green, blue) that produce any color in combination.

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cochlea

A coiled, bony, fluid filled tube in the inner ear through which sound waves trigger nerve impulses.

frequency

The number of complete wavelengths that pass a point in a given time; determines pitch.

basilar membrane

A membrane in the cochlea lined with hair cells that bend in response to sound vibrations.

conductive hearing loss

Hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea.

frequency theory

The theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone.

pitch

A tone’s experienced highness or lowness, which depends on its frequency.

place theory

The theory that links the pitch we hear with the specific area where the cochlea’s membrane is stimulated.

Semicircular canals

Three looped channels in the inner ear that detect head movements and provide a sense of balance.

sensorineural hearing loss

Hearing loss caused by damage to the cochlea’s receptor cells or the auditory nerves.

sound localization

The ability to identify the position and changes in position of sound sources.

Volley theory

The principle that auditory nerve fibers respond to rhythmic sound stimuli in rapid succession to handle high frequencies.

gate control theory

The hypothesis that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to pass.

gustation

The sense of taste, which serves nutritional needs and protects the organism from toxins.

kinesthesis

The system for sensing the position and movement of individual body parts through receptors in muscles and joints.

olfactory system

The structures and processes involved in the detection of and response to odorants (smell).

phantom limb

The feeling that an amputated limb is still present, often manifested as tingling or pain.

pheromones

Chemical signals released outside the body to influence the behavior of other members of the same species.

supertaster

A person with uncommonly low gustatory thresholds and an unusually high number of taste buds.

Taste receptors

Modified epithelial cells (taste buds) found on the tongue and oral cavity.

vestibular sense

The sense of body movement and position, specifically the sense of balance.

Warm/cold receptors

Parts of the somatosensory system concerned with the perception of temperature.

Taste Categories

The five basic tastes: sweet, salty, umami (savory), sour, and bitter, plus oleogustus (fat).

retinal disparity

A binocular cue for perceiving depth; the brain computes distance by comparing images from both retinas.

binocular cues

Depth cues, such as retinal disparity and convergence, that depend on the use of two eyes.

perceptual set

A mental predisposition to perceive one thing and not another.

figure ground

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

monocular cues

Depth cues available to either eye alone, such as interposition and linear perspective.

Gestalt psychology

A psychological approach emphasizing the tendency to integrate pieces of information into meaningful wholes.

bottom up processing

Analysis that begins with the sensory receptors and works up to the brain’s integration of information.

inattentional blindness

Failing to see visible objects when attention is directed elsewhere.

top down processing

Information processing guided by higher level mental processes, expectations, and experience.

selective attention

The process of focusing on particular input while suppressing irrelevant or distracting information.

cocktail party effect

The ability to focus one's attention on a particular stimulus (like a conversation) while filtering out background noise.

Apparent movement

An illusion of motion or change in size of a visual stimulus.

Change blindness

A failure to notice changes in the visual array appearing in two successive scenes.

Closure

The Gestalt principle where people tend to perceive incomplete forms as complete wholes.

Convergence

A binocular cue; the inward rotation of the eyes toward a light source to focus on an object.

Interposition

A monocular cue; when one object partially conceals another, it is perceived as closer.

Linear perspective

A monocular cue; parallel lines appear to converge with distance.

Proximity

The Gestalt principle where objects close to each other are organized into a single perceptual group.

Relative clarity

A monocular cue; sharp, clear objects are seen as closer than hazy, blurred objects.

Relative size

A monocular cue; how large an object is compared to another helps determine distance.

Similarity

The Gestalt principle of grouping items on the basis of shared features or membership in a category.

Texture gradient

A monocular cue; the progressive decline in the resolution of textures as a viewer moves away.

depth perception

The ability to perceive three dimensionality and the distance between the observer and an object.

perceptual constancy

The phenomenon where an object appears unchanged despite variations in stimulus, orientation, or illumination.