AP Psychology Sensation and Perception

Sensation

The process by which sensory receptors (in eye, ear, etc.) receive and are stimulated by stimulus energies from the environment.

Perception

The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

Bottom-up-processing

Analysis that begins with the sense receptors and works up to the brain's processing of the information.

Top-down-processing

Information processing guided by higher-level processes, such as our expectations.

Absolute Threshold

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

Signal Detection Theory

Predicts how and when we detect faint stimuli (dependent on experience, expectations, motivation & fatigue).

Subliminal Stimulation

Stimulation below one's threshold of conscious awareness. Research reveals a subtle, fleeting effect on thinking, but no effect on behavior.

Difference Threshold

The minimum difference between two stimuli required for detection 50% of the time. It is also called the just noticeable difference or JND.

Weber's Law

The difference threshold is in proportion to the strength of the original stimulus.

Sensory Adaptation

Our diminishing sensitivity to unchanging stimuli.

Selective Attention

The focusing of attention on specific stimuli, while ignoring other stimuli (e.g., the cocktail party effect).

Transduction

The transforming of stimulus energies (i.e., light waves, sound waves) into neural impulses.

Wavelength

Distance from the peak of one light or sound wave to the next. Wavelength determines HUE or color in vision and Pitch in audition.

Amplitude

The height of a light or sound wave. It determines brightness in vision and loudness in hearing.

Pupil

Adjustable opening in the center of the eye through which light passes.

Iris

A ring of muscle tissue that forms the colored part of the eye. It controls the size of the pupil.

Lens

The transparent structure behind the pupil that changes shape (called accommodation) to help focus images on the retina.

Visual Acuity

The sharpness of vision.

Nearsightedness

Can see nearby objects more clearly because distant objects focus in front of the retina (eyeball may be too long).

Farsightedness

Can see distant objects more clearly because nearby objects focus behind the retina (eyeball may be too short).

Rods & Cones

The receptor cells for vision. Receptor cells are specialized neurons designed, in this case, to transduce light energy into neural impulses.

Rods

Detect black, white, & gray. Found mainly in the periphery of the retina. More than one rod connects to each bipolar cell. Thus, less light energy is necessary for them to cause the bipolar cells to fire. Necessary for NIGHT VISION & PERIPHERAL VISION.

Cones

Found mainly in the center (fovea) of the retina. Necessary for COLOR VISION and VISUAL ACUITY.

Blindspot

The area in the retina where the optic nerve leaves the back of the eye. No rods or cones are located there, so no vision is possible at that location.

Feature Detectors

Nerve cells in the brain that respond to specific features of a visual stimulus, such as shape, angle, or movement.

Parallel Processing

The ability of the brain to process several aspects of a situation simultaneously.

Young-Helmholtz Trichromatic Theory

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

Opponent Process Theory

Theory that opposing retinal processes (red-green, yellow-blue, & black-white) enable color vision.

Color constancy

Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelength reflected by the object.

Audition

The sense of hearing.

Frequency

The number of complete wavelengths in a given period of time. Frequency determines pitch.

Amplitude

Height of each wavelength--determines loudness.

Sound Localization

Sound waves strike one ear sooner and with more intensity than the other ear. With this information, the brain can determine the location of the sound.

Middle Ear

Chamber between the eardrum and the oval window which contains the ossicles (three tiny bones--hammer, anvil, & stirrup) which concentrate the vibrations of the eardrum.

Inner Ear

Contains the cochlea, semicircular canals, and vestibular sacs.

Cochlea

A coiled, bony, fluid-filled tube through which sound waves trigger nerve impulses.

Basilar Membrane

Membrane along the center of the cochlea that contains hair cells (the receptor cells for sound).

Place Theory

Theory that the pitch we hear is associated with the place where the basilar membrane is stimulated. Best for explaining high-pitched tones.

Frequency Theory

Theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of the tone we are hearing. Best for explaining low-pitched tones.

Volley Principle

Helps explain in frequency theory how we can hear sounds with a frequency greater than 1000 cycles per second.

Conduction Deafness

Caused by damage to the structures that conduct sound waves through the ear (eardrum, ossicles).

Nerve Deafness

Caused by damage to the cochlea's hair cells or the auditory nerve.

Touch

Involves a mixture of at least 4 distinct skin senses--pressure, warmth, cold, and pain.

Gate-Control Theory

Theory that the spinal cord contains a neurological 'gate' that blocks pain signals or allows them to pass.

Taste

The Gustatory Sense, a CHEMICAL SENSE consisting of the four basic tastes of sweet, sour, bitter, & salty.

Taste Buds

Each bump on the tongue contains over 200 taste buds, which reproduce themselves every 2-3 weeks.

Sensory Interaction

The principle that one sense may be influenced by another, as when the smell of food influences its taste.

Smell

The Olfactory Sense, also a CHEMICAL SENSE, capable of detecting about 10,000 different odors.

Kinesthesis

The system for sensing the position and movement of individual body parts.

Vestibular Sense

The system that monitors the head's (and thus the body's) position and movement, providing our sense of equilibrium.

Perception

The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.

Figure-ground Relationship

Our ability to perceive any object (the figure) as distinct from its surroundings (the ground).

Visual Capture

The tendency for vision to dominate the other senses when conflicting information is being received.

Gestalt Organizational Principles

Gestalt psychologists emphasize our tendency to integrate individual pieces of information into a meaningful whole.

Proximity

We group nearby objects as belonging together.

Similarity

Figures similar to each other (i.e., as in shape or color) are grouped together.

Continuity

We perceive smooth, continuous patterns rather than discontinuous ones.

Connectedness

When uniform and linked, we perceive spots, lines, or areas as single units.

Closure

We fill in gaps to create complete, whole objects.

Visual Cliff

A laboratory device for testing depth perception in infants.

Binocular Cues

Depth cues that depend on the use of both of our eyes.

Retinal Disparity

By comparing the two slightly different images received on each retina, the brain computes the distance of what we are looking at.

Convergence

The extent to which the eyes converge inward when looking at an object.

Monocular Cues

Distance cues that require the use of one eye only.

Relative Size

If we assume two objects are about the same size, the one that casts the smaller retinal image is perceived as being farther away.

Interposition (Overlap)

If one object partially blocks another, the one that is partially blocked is perceived to be farther away.

Relative Clarity

Because light from distant objects must pass through more atmosphere, we perceive hazy objects as being farther away than clear, distinct objects.

Texture Gradient

A gradual change from a coarse, distinct texture to a fine, indistinct texture signals increasing distance.

Relative Height

We perceive objects higher in our visual field as being further away.

Linear Perspective

Parallel lines (such as railroad tracks) appear further away as they converge in the distance.

Light & Shadow (relative brightness)

Nearby objects reflect more light. Thus, given two identical objects, the dimmer one seems further away.

Relative Motion (motion parallax)

If while riding in a train you fix your gaze on some object (the fixation point), objects closer than the fixation point appear to be moving backward. The nearer an object is, the faster it seems to move. Objects behind the fixation point appear to be moving with you: The farther away the object is from the fixation point, the more slowly it appears to move.

Motion Perception

One way we perceive motion is by knowing that if an object keeps getting bigger, it is probably moving towards us. If an object is shrinking, it is moving away from us.

Phi Phenomenon

When two or more adjacent stationary lights blink on and off in quick succession, we perceive a single light moving. (Lighted signs use this phenomenon).

Stroboscopic Movement

The brain will interpret a rapid series of slightly varying images as continuous movement. By flashing 24 still pictures each second, a motion picture creates perceived movement.

Perceptual Constancies

Perceiving objects as unchanging (having constant lightness, color, shape, and size) even when our retinal images of them change.

Shape Constancy

We perceive the form of familiar objects as constant even when our retinal images of them change.

Size Constancy

We perceive familiar objects to maintain a constant size even when their distance from us changes.

Lightness Constancy

We perceive an object as having a constant lightness even when its illumination varies.

Sensory Deprivation

People blind from birth, who later have their vision restored, can distinguish figure-ground relationships, can sense colors, but have great difficulty recognizing objects that they were familiar with by touch.

Perceptual Adaptation

In vision, the ability to adjust to an artificially displaced or even inverted visual field.

Perceptual Set

A mental predisposition to perceive one thing and not another (e.g., seeing the Lock Ness Monster instead of a piece of driftwood because of your beliefs).

Context Effects

Any given stimulus may trigger radically different perceptions depending on the surrounding environment or circumstances. Culture may have a great impact on context and perception.

Human Factors Psychology

A branch of psychology that explores how people and machines interact and how machines and physical environments can be adapted to human behaviors.