AP Psychology Unit 4: Sensation and Perception

sensation

sensation

the process by which our sensory receptors and nervous system receive and represent stimulus energies from our 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 sensory receptors and works up to the brain's integration of sensory information.

top-down processing

information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.

selective attention

the focusing of conscious awareness on a particular stimulus.

inattentional blindness

failing to see visible objects when our attention is directed elsewhere.

change blindness

failing to notice changes in the 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 brain can interpret

psychophysics

the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them

absolute threshold

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

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.

subliminal

below one's absolute threshold for conscious awareness.

priming

the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response

difference threshold

the minimum difference between two stimuli required for detection 50 percent of the time. We experience the difference threshold as a just noticeable difference (or jnd).

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)

sensory adaptation

diminished sensitivity as a consequence of constant stimulation

perceptual set

a mental predisposition to perceive one thing and not another

parapsychology

the study of paranormal phenomena, including ESP and psychokinesis

wavelength

the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission

hue

the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth.

intensity

the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave's amplitude

pupil

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

iris

a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening

lens

the transparent structure behind the pupil that changes shape to help focus images on the retina

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

rods

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

cones

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

optic nerve

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

blind spot

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

fovea

the central focal point in the retina, around which the eye's cones cluster

feature detectors

nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement

parallel processing

the processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision. Contrasts with the step-by-step (serial) processing of most computers and of conscious problem solving

Young-Helmholtz trichromatic (three-color)

theory the theory that the retina contains three different 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

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

gestalt

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

figure-ground

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

grouping

the perceptual tendency to organize stimuli into coherent groups

depth perception

the ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance

visual cliff

a laboratory device for testing depth perception in infants and young animals. (Myers Psychology for AP 2e p. 184) Indicates some depth perception is innate.

binocular cues

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

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

monocular cues

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

phi phenomenon

an illusion of movement created when two or more adjacent lights blink on and off in quick succession

perceptual constancy

perceiving objects as unchanging (having consistent shapes, size, brightness, and color) even as illumination and retinal images change

color constancy

perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

perceptual adaptation

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

audition

the sense or act of hearing

frequency

the number of complete wavelengths that pass a point in a given time (for example, per second)

pitch

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

middle ear

the chamber between the eardrum and cochlea containing three tiny bones (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrum on the cochlea's oval window

cochlea

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

inner ear

the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs

sensorineural hearing loss

hearing loss caused by damage to the cochlea's receptor cells or to the auditory nerves. (Also called nerve deafness.)

conduction hearing loss

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

cochlear implant

a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea

place theory

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

frequency theory

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.

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.

kinesthesia

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

vestibular sense

the sense of body movement and position, including the sense of balance.

sensory interaction

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

cornea

Anatomy of the eye: outermost transparent layer protecting the eye; assists in light refraction

bipolar cells

A type of retinal cells that accepts electric (nerve) impulses from the photoreceptors and passes them to the ganglion cells

ganglion cells of the eye

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

auditory canal

channel that leads from the pinna to the eardrum

basilar membrane

A structure that runs the length of the cochlea in the inner ear and holds the auditory receptors, called hair cells.

papillae

Bumps on the tongue that contain taste buds, the receptors for taste.

umani

a fifth taste sensation added to the list, a savory flavor

semicircular canal

Passages in the inner ear associated with maintaining equilibrium

cocktail party effect

The ability to focus on one auditory message and ignore others; also refers to the tendency to notice when your name suddenly appears in a message that you've been actively ignoring

law of similarity

The Gestalt principle that we tend to group similar objects together in our perceptions.

law of proximity

Elements located close to one another are perceived as belonging to the same figure

law of closure

the tendency to fill in the gaps in an incomplete image.

"visual cliff"

Babies between 6.5 and 12 month of age were reluctant to crawl over the "cliff" edge, even when called by their mothers, suggesting that they perceived the drop created by the check pattern.

monocular depth cues

Features of the visual stimulus that indicate distance even if the stimulus is viewed with only one eye.

linear perspective

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

aerial perspective

Monocular cue to distance and depth based on the fact that more distant objects are likely to appear hazy and blurred.

relative size

The monocular cue that states that if an object seems larger, it is probably closer, and if an object is smaller, it is probably distant.

motion parallax

A depth cue whereby a difference in the apparent rate of movement of different objects provides information about the relative distance of those objects

binocular depth cues

Clues about distance based on the differing views of the two eyes

amplitude

Height of a wave

accommodation

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

subliminal perception

Perception below the threshold of awareness.

Young-Helmholtz theory

the theory that the retina contains three different 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.

location detection

if a sound occurs right in front of you it hits both your ears at the same time. Otherwise it hits one before the other. Using that time difference the body can determine the location of the sound. Called Coincidence Detection. Neurons can also detect difference in volume. These both work for LEFT RIGHT locating. Cells in the superior olive.

olfaction

sense of smell

phantom limb

sensations that appear to originate in a limb that has been amputated after an amputation, the person continues to experience the felt presence of the amputated limb. what happens is the region of the parietal lobe that normally receives signals from the amputated limb is no longer getting that input so neurons form connections with neurons in adjacent regions of the body map and because of this neuroplastic reorganization, the phantom limb is born.

Ponzo illusion

An illusion of size in which two objects of equal size that are positioned between two converging lines appear to be different in size. Also called the railroad track illusion.

stroboscopic movement

the brain's perception of continuous movement in a rapid series of slightly varying images; this is how we perceive motion in film and animation

interposition

monocular visual cue in which two objects are in the same line of vision and one patially conceals the other, indicating that the first object concealed is further away

perceptual set

The interpretation of ambiguous sensory information in terms of how our past experiences have set us to perceive it.

context effects

a given stimulus may trigger radically different perceptions, partly because of our differing set, but also because of the immediate context. Culture or previous experiences can influence how we perceive our situations.

moon illusion

The Moon looks up to 50% larger when near the horizon than when it is high in the sky.

Cilia

are microscopic, hair-like structures on the surface of cells that beat in unison to create movement. In our ears, sound waves stimulate motion of the structure, which sends a message to our brain that we are hearing sound. They also keep our airways clean by removing mucus and dust from the nose and lungs.

nocieptors

sensory receptors that detect hurtful temperatures, pressure, or chemicals