AP Psychology: Sensation & Perception (Modules 1.6a–2.1b)

Sensation

The process by which sensory receptors detect physical stimulation and transmit that information to the brain.

Perception

The process by which the brain organizes and interprets sensory information.

Bottom-up processing

Analysis that begins with sensory receptors and builds toward recognition.

Transduction

The conversion of one form of physical energy, such as light or sound, into neural impulses.

Absolute threshold

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

Signal detection theory

The theory that detecting a weak stimulus depends on signal strength and psychological factors such as expectations, motivation, experience, and alertness.

Subliminal stimulus

A stimulus below the absolute threshold for conscious awareness.

Priming

The activation of associations that influences later thoughts, perceptions, or behavior.

Difference threshold (JND)

The minimum difference between two stimuli that can be detected 50 percent of the time.

Weber's law

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

Sensory adaptation

Diminished sensitivity after constant exposure to an unchanging stimulus, which frees attention for new or changing information.

Wavelength

The distance between wave peaks; for light, it determines perceived hue, and for sound it is inversely related to frequency and pitch.

Amplitude

The height of a wave; it determines brightness for light and loudness for sound.

Cornea

The transparent outer surface of the eye that bends incoming light to help focus it.

Pupil

The adjustable opening in the eye through which light enters.

Iris

The colored muscle that controls the size of the pupil.

Lens

The transparent eye structure that changes shape to focus images on the retina.

Accommodation

The process by which the lens changes curvature and thickness to focus near or distant objects on the retina.

Retina

The light-sensitive inner surface at the back of the eye containing rods and cones.

Myopia

Nearsightedness caused when distant images focus in front of the retina.

Farsightedness

A condition in which nearby images focus behind the retina.

Cones

Retinal receptors concentrated near the fovea that detect color and fine detail and work best in bright light.

Rods

Retinal receptors concentrated in the periphery that detect dim light, black-and-white vision, and peripheral motion.

Fovea

The central area of the retina where cones cluster and visual detail is sharpest.

Blind spot

The point where the optic nerve leaves the eye; it contains no receptor cells.

Visual pathway

Rods and cones activate bipolar cells, which activate ganglion cells; their axons form the optic nerve, which carries information through the thalamus to the visual cortex.

Young-Helmholtz trichromatic theory

The theory that three types of cones, primarily sensitive to red, green, and blue, combine their activity to produce color vision.

Opponent-process theory

The theory that color is processed in opposing red-green, blue-yellow, and white-black channels; it explains negative afterimages.

Feature detectors

Specialized neurons in the visual cortex of the occipital lobe that respond to edges, lines, angles, and movement.

Parallel processing

The brain's simultaneous processing of several aspects of a visual scene, including color, motion, form, and depth.

Frequency

The number of complete waves per second, measured in hertz; for sound, it determines pitch.

Pitch

The perceived highness or lowness of a sound, primarily determined by frequency.

Auditory pathway

Sound travels through the auditory canal to the eardrum, middle-ear bones, oval window, cochlear fluid, basilar membrane and hair cells, auditory nerve, thalamus, and auditory cortex.

Hammer, anvil, and stirrup

The three middle-ear bones that amplify and transmit vibrations from the eardrum to the oval window.

Cochlea

A fluid-filled, snail-shaped inner-ear structure containing the basilar membrane and hair cells used in hearing.

Auditory hair cells

Receptor cells in the cochlea whose movement triggers neural impulses in nearby nerve cells.

Conduction hearing loss

Hearing loss caused by damage to the mechanical system that transmits sound to the cochlea, such as the eardrum or middle-ear bones.

Sensorineural hearing loss

Hearing loss caused by damage to the cochlea's hair cells or the auditory nerve.

Cochlear implant

A device that converts sounds into electrical signals and transmits them toward the auditory nerve.

Place theory

The theory that pitch depends on which location along the basilar membrane is activated; it best explains high pitches.

Frequency theory

The theory that pitch is represented by neural impulses matching a sound wave's frequency; it best explains low pitches.

Volley theory

The theory that groups of neurons alternate firing so their combined activity represents frequencies too fast for one neuron.

Sound localization

The brain's use of differences in arrival time and intensity between the two ears to locate a sound's direction.

Touch

A mixture of four basic skin sensations: pressure, warmth, cold, and pain.

Biopsychosocial model of pain

The view that pain reflects interacting biological, psychological, and social-cultural influences.

Nociceptors

Sensory receptors that detect potentially harmful temperature, pressure, or chemicals and send pain signals.

Gate-control theory

The theory that a spinal-cord gate regulates pain signals; small fibers tend to open it, while large-fiber activity and brain messages can help close it.

Placebo effect

A change caused by expectations after an inactive treatment; pain relief may partly involve endorphin release.

Endorphins

The body's natural painkillers, which can reduce the experience of pain.

Gustation

The chemical sense of taste.

Six basic tastes

Sweet, sour, salty, bitter, umami, and oleogustus, the taste of fat.

Olfaction

The chemical sense of smell.

Olfactory pathway

Odor molecules activate receptor combinations that send signals to the olfactory bulb and then to areas involved in smell, memory, and emotion; the pathway initially bypasses the thalamus.

Kinesthesia

Awareness of the position and movement of individual body parts.

Proprioceptors

Position and motion receptors located in muscles, tendons, and joints that support kinesthesia.

Vestibular sense

The sense of balance and the position and movement of the head and body.

Semicircular canals and vestibular sacs

Inner-ear structures containing receptors that detect head movement and support balance.

Sensory interaction

The principle that one sense can influence another, such as smell affecting taste or vision affecting hearing.

McGurk effect

The perception of a third speech sound when visible lip movements conflict with the sound being heard.

Synesthesia

A condition in which stimulation of one sense automatically produces an experience in another sense.

Embodied cognition

The influence of bodily sensations, gestures, and physical states on thoughts and judgments.

Selective attention

Focusing conscious awareness on one stimulus while filtering out others.

Cocktail-party effect

The ability to attend to one voice among many while important information, such as one's name, can capture attention.

Inattentional blindness

Failing to notice a visible object because attention is directed elsewhere.

Change blindness

Failing to notice a change in the environment.

Perceptual set

A mental predisposition to perceive a stimulus in a particular way, shaped by experience and expectations.

Gestalt psychology

The approach emphasizing that the brain organizes sensory fragments into meaningful wholes and that the whole may exceed the sum of its parts.

Figure-ground

The organization of perception into an attended object, the figure, and its surrounding background, the ground.

Proximity

The Gestalt principle that nearby objects are grouped together.

Similarity

The Gestalt principle that similar-looking objects are grouped together.

Closure

The Gestalt principle that the brain fills gaps to perceive complete forms.

Depth perception

The ability to perceive objects in three dimensions and estimate their distance.

Visual cliff

An experimental apparatus that operationally measures depth perception by whether an infant or young animal avoids an apparent drop-off.

Binocular cues

Depth cues requiring information from both eyes, including retinal disparity and convergence.

Retinal disparity

A binocular cue based on the difference between the images received by the two eyes; greater disparity usually signals a closer object.

Convergence

A binocular cue based on how strongly the eyes turn inward when focusing on a nearby object.

Monocular cues

Depth cues available to either eye alone.

Relative size

A monocular cue in which the smaller retinal image of two assumed-similar objects is perceived as farther away.

Interposition

A monocular cue in which an object that partially blocks another is perceived as closer.

Linear perspective

A monocular cue in which parallel lines appear to converge as distance increases.

Texture gradient

A monocular cue in which texture becomes finer and smoother as distance increases.

Relative clarity

A monocular cue in which hazier objects appear farther away.

Stroboscopic movement

The illusion of continuous movement created by a rapid sequence of slightly different still images, as in movies.

Phi phenomenon

The illusion that one light is moving when adjacent stationary lights flash in sequence.

Autokinetic effect

The illusion that a stationary point of light moves when viewed in complete darkness without reference points.

Perceptual constancy

The perception of objects as stable despite changes in sensory input.

Color constancy

Perceiving an object's color as relatively stable under changing illumination.

Brightness constancy

Perceiving brightness in relation to surrounding objects and lighting context.

Shape constancy

Perceiving a familiar object's shape as stable despite changes in its retinal image.

Size constancy

Perceiving an object's size as stable despite changes in distance and retinal-image size.

Critical period

An early developmental window during which certain sensory experiences are necessary for normal perceptual development.

Sensory restriction

Lack of needed early sensory stimulation, which can prevent normal neural and perceptual development.

Restored vision

Vision gained after prolonged blindness; research shows that some visual organization is present but object recognition often requires experience.

Perceptual adaptation

The ability to adjust to changed sensory input, such as shifted or inverted vision.

Top-down processing

your expectations and prior knowledge help interpret sensory information.