Psych Unit 7

sensation

sensation

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

sensory receptors

sensory nerve endings that respond to stimuli

perception

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

• brings meaning to sensation; produces an interpretation of the world, but it isn’t a perfect representation

bottom-up processing

analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information (relying on senses ONLY)

top-down processing

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

• reading your friend’s text with a lot of typos and knowing what it means

selective attention

the focusing of conscious awareness on a particular stimulus (minute detail)

cocktail party effect

the ability to attend to one voice among a sea of other voices (while also being able to detect your own name)

inattentional blindness

failing to see visible objects when our attention is directed elsewhere

change blindness

failing to notice changes in the environment; a form of inattentional blindness

transduction

conversion of one form of energy into another; the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret

1. receive: sensory neurons (receptors)

2. transform: interneurons (processed by brain and spinal cord)

3. deliver: motor neurons (physiological response)

absolute threshold

the minimum stimulus energy needed to detect a particular stimulus 50% of the time

• because there is a fuzzy line between detection and nondetection, a person’s threshold is not necessarily absolute; it varies continuously with our mental alertness and physical condition (signal detection theory)

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

says sensation depends on the characteristics of the stimulus, background, and detector

• takes observer’s characteristics into account, says stimulus judgment is often unconscious

• some people can detect certain things more easily than others

subliminal

below one’s absolute threshold for conscious awareness

difference threshold (just noticeable threshold)

the minimum difference between 2 stimuli required for detection 50% of the time (minimum that is still recognizable)

priming

activates unconscious associations; used by researches

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)

the size of the just-noticeable difference is proportional to the intensity of the stimulus; the just-noticeable difference is large when the intesntiy of the stimulus is high

sensory adaptation

diminished sensitivity as a consequence of constant stimulation

wavelength

the distance from the peak of one light or sound wave to the peak of the next; electromagnetic ones vary from the short blips of gamma 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 wave or sound wave, which influences what we perceive as brightness or loudness; determined by the wave’s amplitude

cornea

the eye’s clear, protective outer layer, covering the pupil and iris; transparent tissue where light enters the eye

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; expands and contracts to change the size of the pupil for light

lens

the transparent structure behind the pupil that changes shape to help focus images on the retina; focuses the light rays on the retina through accommodation

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

fovea

the central focal point in the retina, around which the eye’s cones cluster; area of sharpest vision; has highest concentration of cones (NO RODS)

accommodation

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

rods

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

• especially sensitive to dim light, but not color

cones

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

• especially sensitive to colors, but not dim light

  • responsible for our ability to “see” colors

path light travels

rods/cones (retina)

bipolar cells

ganglion cells

optic nerve

thalamus

occipital lobe

optic nerve

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

• this is where the stimulus, once changed into a neural impulse, gets passed onto the brain

blind spot

the point at which the optic nerve leaves the eye, creating a “blind” spot because no photoreceptors are located there

Young-Helmholtz trichromatic theory

the theory that the retina contains 3 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

opponent-process theory

the theory that opposing retinal processes (red-green, blue-yellow, 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

there are some color combos we never see (e.g. reddish-green or yellowish-blue)

• color perception is controlled by the activity of 2 opponent systems; a blue-yellow mechanism and a red-green mechanism

feature detectors

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

parallel processing

processing many aspects of a problem simultaneously; the brain’s natural mode of information processing for many functions

audition

the sense or act of hearing

amplitude

the physical strength of a wave (the “volume” of the sound)

frequency

the number of complete wavelengths that pass a point in a given time (determines pitch)

pitch

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

decibels

a logarithmic unuit that expresses the ratio of acoustic or electric power (intensity)

eardrum

middle ear

the chamber between the eardrum and cochlea containing 3 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

• contains auditory receptors for hearing

inner ear

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

basilar membrane

hair cells

auditory nerve

auditory cortex

sensorineural hearing loss

hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves; the most common form of hearing loss

conduction hearing loss

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

cochlear implant

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

tactile sense

sense of touch

bottom-up cognition of pain

top-down cognition of pain

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 sensation

misinterpretation of the spontaneous central nervous system activity that occurs in the absence of normal sensory input

endorphins

placebo

gustation

sense of taste

• specialized nerves carry nothing but the taste messages to the brain; there, taste is realized on a specialized region of the parietal lobe’s somatosensory cortex

• taste receptors can easily be damaged by alcohol, smoke, acids, or hot foods

• gustatory receptors are frequently replaced

olfaction

sense of smell

• odons first interact with receptor proteins associated with hairs in the nose

• hairs convey information to the brain’s olfactory bulbs, located on the underside of the brain (bypasses thalamus)

kinesthesia

our movement sense—our system for sensing the position and movement of individual body arts

vestibular sense

our sense of body movement and position that enables our sense of balance

• receptors for this info are tiny hairs in the semicircular canal of the inner ear (info sent to the cerebellum)

sensory interaction

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

McGurk effect

embodied cognition

gestalt

an organized whole; these psychologists emphasized our tendency to integrate pieces of information into meaningful wholes

• divides perceptual experience into figure and ground

figure-ground

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

grouping

the perceptual tendency to organize stimuli into coherent groups

after distinguishing the figure from the ground, our perception needs to organize the figure into a meaningful form using grouping rules

proximity

we group nearby figures together; we see not six separate lines, but three sets of two lines

continuity

we perceive smooth, continuous patterns rather than discontinuous ones; this pattern could be a series of alternating semicircles, but we perceive it as two continuous lines—one wavy, one straight

closure

we fill in gaps to create a complete, whole object, thus we assume that the circles on the left are complete but partially blocked by the (illusory) triangle; add nothing more than little line segments to close off the circles and your brain stops constructing a triangle

both visual and auditory stimuli

• similarity, proximity, continuity

depth perception

the ability to see objects in 3 dimensions although the images that strike the retina are 2-dimensional; allows us to judge distance

visual cliff

a laboratory device for testing depth perception in infants and young animals

binocular cues

a depth cue, such as retinal disparity, that depends on the use of two eyes

retinal disparity

a binocular cue for perceiving depth; by comparing retinal images from the 2 eyes, the brain computes distance — the greater the disparity between the 2 images, the closer the object

monocular cues

a depth cue, such as interposition or linear perspective, available to each eye alone

relative height

monocular cue; we perceive objects higher in our field of vision as farther away

relative motion

monocular cue; as we move, objects that are actually stable may appear to move

relative size

monocular cue; if we assume 2 objects are similar in size, most people perceive the one that casts the smaller retinal image as farther away

linear perspective

monocular cue; parallel lines appear to meet in the distance (the sharper the angle of convergence, the greater the perceived distance)

interposition

monocular cue; if one object partially blocks our view of another, we perceive it as closer

light and shadow

monocular cue; shading produces a sense of depth consistent with our assumption that light comes from above

motion perception

the process of inferring the speed and direction of elements in a scene based on visual input

stroboscopic movement

our brain perceiving a rapid series of slightly varying images as continuous movement

phi phenomenon

an illusion of movement created when 2 or more adjacent lights blink on and off in quick succession

perceptual constancy

the ability to recognize the same object as remaining “constant” under changing conditions

color constancy

perceiving familiar objects as having consistent color even when changing illumination filters the light reflected by the object

lightness constancy

ability to perceive the relative reflectance of objects despite changes in illumination

relative luminance

the amount of light a objects reflects on its surroundings

shape constancy

the tendency for a familiar object's shape to be perceived as constant when observed from various angles, positions and orientations

size constancy

the perception of an object or quality as constant even though our sensation of the object changes

perceptual adaptation

the ability to adjust to changed sensory input, including an artificially displaced or even inverted visual field

perceptual set

a mental predisposition to perceive one thing and not another

schema

concepts in our brain that organize and interpret unfamiliar information

context

the situation/circumstances in which an event occurs

extrasensory perception (ESP)

the controversial claim that perception can occur apart from sensory input

telepathy

mind-to-mind communication

clairvoyance

perceiving remote events, such as a house on fire in another state

precognition

perceiving future events, such as an unexpected death in the next moth