AP Psychology U3 - Sensation and Perception

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

predicts how and when we detect the presence of 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.

Extrasensory perception (ESP)

the controversial claim that perception can occur apart from sensory input; includes telepathy clairvoyance and precognition.

Parapsychology

the study of paranormal phenomena including ESP and psychokinesis.

Audition

the sense or act of hearing.

Sound wave

changes in pressure generated by vibrating molecules.

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.

Decibels

unit we measure sounds in.

Hertz

the unit of frequency equal to one cycle per second.

Outer ear

visible part of ear.

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.

Hammer, Anvil, Stirrup

three tiny bones in the middle ear that transmits vibrations to the cochlea.

Eardrum

a conically shaped membrane that separates the external ear from the middle ear and serves to transform the pressure waves of sounds into mechanical vibration of the ossicles.

Round window

a membrane-covered opening in the cochlea where it borders the middle ear.

Oval window

a membrane-covered opening in the bony wall of the cochlea in the ear.

Inner ear

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

Cochlea

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

Basilar membrane

a fibrous membrane within the cochlea that supports the organ of Corti. In response to sound the basilar membrane vibrates; this leads to stimulation of the hair cells—the auditory receptors within the organ of Corti.

Organ of Corti/Hair cells

a specialized structure that sits on the basilar membrane within the cochlea in the inner ear. It contains the hair cells (the sensory receptors for hearing) their nerve endings and supporting cells.

Semicircular canals

a set of three looped tubular channels in the inner ear that detect movements of the head and provide the sense of dynamic equilibrium that is essential for maintaining balance.

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 implants

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.

Touch

the ability to perceive an object or other stimulus that comes into contact with the surface of the skin.

Pain

an unpleasant sensory and emotional experience associated with damage to nerve tissue, stimulation of free nerve endings, or excessive stimulation.

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.

Phantom limb

a condition in which patients experience sensations, whether painful or otherwise, in a limb that does not exist.

Taste

the sense devoted to the detection of molecules dissolved in liquids.

Basic tastes

sweet, salty, sour, bitter, umami.

Smell/olfaction

the sense that enables an organism to detect the odors of volatile substances. Molecules of odorant chemicals carried by air currents are absorbed into nasal mucus and stimulate the olfactory receptors, where they are converted to neural messages.

Olfactory nerve

the first cranial nerve, which carries sensory fibers concerned with the sense of smell. It originates in the olfactory lobe and is distributed to olfactory receptors in the nasal mucous membrane.

Olfactory bulb

structure located in the forebrain of vertebrates that receives neural input about odours detected by cells in the nasal cavity.

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.

Embodied cognition

in psychological science, the influence of bodily sensations, gestures, and other states on cognitive preferences and judgments.

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.

Proximity

we group nearby figures together.

Continuity

we perceive smooth, continuous patterns rather than discontinuous ones.

Closure

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

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.

Binocular cues

depth cues, such as retinal disparity, that depend on the use of two eyes.

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.

Linear perspective

one of the monocular depth cues, arising from the principle that the size of an object's visual image is a function of its distance from the eye.

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.

Sensory deprivation

the lack of sensory stimulation, either by natural causes in cases of blindness or deafness, or in experimental settings.

Perceptual adaptation

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

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.

Cornea

protects the eye and bends light to provide focus; light first enters through this.

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.

Accomodation

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

Myopia

nearsightedness

Hyperopia

farsightedness

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.

Optic chiasm

the part of the brain where optic nerves cross and is therefore of primary importance to the visual pathway.

Bipolar cells

a type of nerve cells that combine the impulses from many of the visual receptor cells in the retina and then transmits those impulses to the ganglion cells.

Ganglion cells

neurons that relay information from the retina to the brain via the optic nerve.

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.

After-image effect

visual illusion in which retinal impressions persist after the removal of a stimulus.