Unit 4: Basic Principles of Sensation and Perception

Prosopagnosia

inability to recognize faces; due to brain being unable to put visual info together into a gestalt

Sensation

the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment; eg: light waves, sound waves, pressure, chemicals, etc.

Perception

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

memory, motivation, emotion, and culture

perception is influenced by our...

psychophysics

the study of relationships between the physical characteristics of stimuli (energy of the world) and our psychological experience of them (our perception)

Bottom-up processing (feature analysis)

analysis that begins with the sensory receptors and works up to the brain's integration of sensory information; used when you experience something for the first time

top-down processing

information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations; prior experience allows us to create schemata

schemata

a pattern of thought or behavior that organizes categories of information and the relationships among them

perceptual set

a mental predisposition to perceive one thing and not another; created by the existence of a schema; ex: seeing shapes in clouds

backmasking

supposed hidden messages musicians recorded backward in their music

selective attention

the focusing of conscious awareness on a particular stimulus; our awareness focuses on a minute aspect of all that we experience

cocktail party effect

ability to attend to only one voice among many

selective inattention

what we are not focused on, what we do not notice; ex: inattentional blindness, change blindness, change deafness, choice blindness, pop-out phenomenon

inattentional blindness

failing to see visible objects when our attention is directed elsewhere

absolute threshold

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

subliminal stimulus

a stimulus that is below the threshold of conscious awareness; can't affect our behavior but can prime

priming

the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response; ex: music you like playing in the background can change your mood

difference threshold (just noticeable difference)

the minimum difference between two stimuli required for detection 50 percent of the time

Weber's Law (Weber-Fechner Law)

to be perceived as different, two stimuli must differ by a constant minimum percentage

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 receiver operating characteristics

receiver operating characteristics

a person's experiences, expectations, motivation, and alertness

false positive

when we think we perceive a stimulus that is not there

false negative

not perceiving a stimulus that is present

sensory adaptation (habituation)

diminished sensitivity to an unchanging stimulus; happens to all of our senses except vision

Vision Step 1 Gathering light

light is reflected off objects and gathered by the eye

wavelength

determines hue (ROY G BIV)

intensity

determines brightness/amplitude

transduction

the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brains can interpret

black, white

objects appear _____ because they absorb all colors and _____ because they reflect all wavelengths of light

Vision Step 2 Within Eye

when we look at something, we turn our eyes toward the object and the reflected light coming from the object enters our eye

cornea

acts as protection for the outer layer of your eye and bends light to provide focus

iris

surrounds and controls the size of the pupil; dilates or constricts in response to light intensity and emotions

pupil

small adjustable opening that light passes through

lens

helps focus light rays into images

retina

contains the receptor rods, cones, and layers of neurons that begin the processing of visual information

fovea

where light is being focused (center of your vision)

rods

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

cones

retinal receptor cells that are concentrated near the center of the retina (in the fovea) and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations.

blind spot

where the optic nerve leaves the eye and there are no receptor cells

normal vision

pure light strikes retina

nearsighted

a condition in which nearby objects are seen more clearly than distant objects because distant objects focus in front of the retina

farsighted

a condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind the retina

Vision Step 3 Transduction

occurs when light activates the neurons in the retina; activation of rods and cones -> act. bipolar cells -> act. ganglion cells (optic nerve) -> sends these impulses to lateral geniculate nucleus region of the thalamus

Vision Step 4 In the Brain

the visual cortex is located in the occipital lobe; impulses from the cells of the retina activate feature detectors

feature detectors

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

David Hubel and Torsten Wiesel

discovered feature detectors

parallel processing

our brain's ability to process multiple things at once; processes color, motion, form, and depth

Young-Helmotz trichromatic (3 color) theory

the theory that the retina contains different color receptors that can produce the perception of any color if it can be created with a combination of red, green, and blue light

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

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

objects that are close together are more likely to be perceived as belonging in the same group

similarity

objects that are similar in appearance are more likely to be perceived as belonging in the same group; ex: racism

continuity

objects that form a continuous form are more likely to be perceived as belonging in the same group

closure

objects that make up a recognizable image are more likely to be perceived as belonging in the same group even if the image contains gaps that the mind needs to fill in

perceptual constancy

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

color constancy

the tendency for a color to look the same under widely different viewing conditions; ex: snow still looks white when wearing pink tinted ski goggles

brightness constancy (lightness constancy)

the tendency to perceive the apparent brightness of an object as the same even when the light conditions change; ex: we expect objects in shadow to be lighter than they seem

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

Eleanor Gibson and Richard Walk

developed the visual cliff to test depth perception

monocular cues

depth cues available to either eye alone; relative height, rel. size, interposition, rel. clarity, texture gradient, rel. motion, linear perspective, light and shadow

binocular cues

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

convergence

A binocular cue for perceiving depth; the extent to which the eyes converge inward when looking at an object (more inward as it gets closer)

retinal disparity

each of our eyes sees any object from a slightly different angle; closer = more disparity

Muller-Lyer Illusion

illusion of line length that is distorted by inward-turning or outward-turning corners on the ends of the lines, causing lines of equal length to appear to be different

Ponzo Illusion

two objects of equal size that are positioned between two converging lines appear to be different in size (railroad track illusion)

Moon Illusion

A visual illusion involving the misperception that the moon is larger when it is on the horizon than when it is directly overhead.

motion

motion perception involves our brain's ability to detect how fast images move across our retinas and to take into account our own movement

stroboscopic movement

the brain perceives continuous movement in a rapid series of slightly varying images (24 still images per sec)

Phi Phenomenon

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

Autokinetic Effect

a small, stationary light in an otherwise dark or featureless environment will appear to move or drift because there are no surrounding cues to indicate that the light is not moving

perceptual adaptation

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

George Stratton

studied sensory adaptation using inversion goggles he invented

Frequency

wavelength that determines the pitch (megahertz)

Amplitude

loudness/intensity of a sound wave (decibels); 85 decibels is threshold

outer ear (pinna)

collects sound from air and directs it through the ear/auditory canal to the eardrum (tympanic membrane)

middle ear

channels the sound through the ossicals (3 tiny bones) to the oval window in the inner ear

ossicals

hammer (malleus), anvil (incus), stirrup (stapes)

inner ear

vibrations of the oval window -> cochlea

cochlea

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

basilar membrane

lined with hair cells connected to the organ of Corti

organ of Corti

neurons activated by movement of hair cells, cause transduction

place theory

the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated; explains high pitched sounds

frequency theory

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 (hair cells fire at diff frequencies); low pitched sounds

conductional deafness

something mechanical in your ears causes hearing loss; ex: foreign objects, fluid, allergies, ear wax, ruptured eardrum

conventional hearing aids

may restore hearing by amplifying the vibrations conducted by other facial bones to the cochlea

sensorineural hearing loss

hearing loss caused by damage to the cochlea's receptor cells or to the auditory nerves; caused by sounds above 85 decibals

cochlear implants

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

sound localization

the process by which you determine the location of a sound; relies on stereophonic hearing and parallel processing

Somatosensation (touch)

activated by indentation (pressure), piercing (pain), or experiences a change in temp (warmth/cold)

nociception

pain signaling explained using gate-control theory

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.

gustation (taste)

nerves respond to chemicals rather than to energy

papillae

where taste buds are located; more densely packed taste buds = more intense flavor

5 types of tastes

sweet, salty, sour, bitter, umami

olfaction (smell)

olfactory nerves respond to chemicals rather than energy

sensory interaction

why food tastes better in a good smelling room

vestibular sense

the sense of body movement and position in space, including the sense of balance; 3 semicircular canals (fluid filled tubes) in the inner ear give the brain feedback about body orientation depending on where the fluid is touching

kinesthetic sense

gives us feedback about the position and orientation of specific body parts; ex: you can close your eyes and touch your kneecap

extrasensory perception (ESP)

the ability to perceive a sensation "outside" the scientifically recognized senses