AP PSYCH:

Sensory adaptation

Diminished sensitivity as a consequence of constant stimulation.

Sensation

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

Perception

The process by which our brain organizes and interprets sensory information, enabling us to recognize objects and events as meaningful.

Absolute threshold

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

Weber’s law

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

Signal detection theory

A theory predicting how and when we detect the presence of a faint stimulus—signal—amid background stimulation—noise; assumes there is no single absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and alertness.

Cornea

The eye’s clear, protective outer layer, covering the pupil and iris.

Pupil

The adjustable opening in the center of the eye through which light enters.

Retina

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

Optic nerve

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

Rods

Retinal receptors that detect black, white, and gray, and are sensitive to movement. Rods are necessary for peripheral and twilight vision, when cones don’t respond.

Cones

Retinal receptors that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. Cones detect fine detail and give rise to color sensations.

Young–Helmholtz trichromatic theory

The theory that the retina contains three different types of color receptors—one most sensitive to red, one to green, one to blue—which, when stimulated in combination, can produce the perception of any color.

Amplitude (in Hearing)

The height, or amplitude, of sound waves determines their perceived loudness.

Frequency (in Hearing)

The number of complete wavelengths that pass a point in a given time—for example, per second.

Cochlea

A coiled, bony, fluid-filled tube in the inner ear; sound waves traveling through the cochlear fluid trigger nerve impulses.

Frequency theory (in Hearing)

In hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch. Also called temporal coding.

Gate-control theory

The theory that the spinal cord contains a neurological ‘gate’ that blocks pain signals or allows them to pass on to the brain. The ‘gate’ is opened by the activity of pain signals traveling up small nerve fibers, and is closed by activity in larger fibers or by information coming from the brain.

Olfaction

Our sense of smell.

Gestalt rules

Gestalt psychologists identified rules our minds use to organize stimuli into meaningful wholes.

Proximity (Gestalt)

We group nearby figures together.

Similarity (Gestalt)

We group objects according to how similar they are to each other.

Closure (Gestalt)

We fill in gaps to create a complete, whole object.

Gestalt (General)

An organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes.