Chapter 4: Sensation, Attention, and Perception

transducers

convert 1 type of energy into another

sensation

conversion of energy from environment into pattern of response by nervous system

psychophysics

how mind interprets physical properties of stimuli

absolute threshold

minimum amount of physical energy that can be detected 50% of the time

• ex. humming noise may fall below threshold for old man

difference threshold

minimum difference in physical energy between 2 stimuli that can be detected 50% of the time

• ex. how many extra grains of sugar to notice different taste in coffee

sensory adaptation

decrease over time in sensory response to unchanging stimuli

• ex. no longer smelling a bad smell after being in the area for a while

perceptual features

basic attributes of a stimulus

• ex. lines, shapes, colours, edges

feature detector

cells in cortex that respond to specific attributes of an object

hue

colour of light as determined by its wave length

cornea

curved, transparent protective layer of the eye that light enters through

lens

clear structure behind pupil that bends light towards retina

accommodation

changes in shape of lens to enable seeing close or far objects

hyperopia

difficulty focusing on nearby objects

myopia

difficulty focusing on distant objects

astigmatism

defects in cornea that cause unfocused vision

presbyopia

farsightedness caused by aging

retina

surface at back of eye that lens focuses light rays onto

cones

sensitive to colour and work best in bright light

rods

for dim light and produce only black & white sensations

visual activity

sharpness of visual perception

blind spot

area in retina where optic nerve exists that contains no photoreceptor skills

optic nerve

structure that conveys visual info away from retina to brain

fovea

tiny spot in centre of retina that contains only cones and visual acuity is greatest

dark adaptation

increased light sensitivity of eye under low-light conditions

pupil

black opening inside iris that allows light in

trichromatic theory of colour vision

based on 3 cone types: red, green, blue

opponent-process theory of colour vision

colour vision is based on coding things as red or green, yellow or blue, black or white (either-or messages)

pitch

high or loud tune sounds, frequency of sound wave

loudness

volume, related to amplitude of sound wave

eardrum

membrane that vibrates in response to sound waves and transmits them inwards

cochlea

snail-shaped organ in inner ear containing sensory receptors for hearing

basilar membrane

structure in cochlea containing hair cells that convert sound waves into action potentials

hair cells

receptor cells within cochlea that transduce vibrations into nerve impulses

conductive hearing loss

poor transfer of sounds from eardrum to inner ear

sensorineural hearing loss

damage to inner-ear hair cells or auditory nerve

noise-induced hearing loss

exposing hair cells to excessively loud sounds

frequency theory of hearing

pitch is decoded from rate at which hair cells of the basilar membrane are firing

place theory of hearing

higher & lower tones excite specific areas of cochlea

olfaction

smell

gustation

taste

skin senses

touch, pressure, pain, heat, cold

kinesthetic senses

body movement and positioning

vestibular senses

perception of balance, gravity and acceleration

lock and key theory of olfaction

odors are related to shapes of chemical molecules

• ex. floral, minty etc

taste buds

receptor cells for taste

warning system

pain based on large nerve fibres, warns body of incoming pain

• without this, unable to prevent injury

reminding system

pain based on small nerve fibres; reminds brain that body has been injured

• ex. lower back pain

gate control theory

pain messages pass through neural gates in spinal cord

multimodal integration

brain combines info coming from multiple senses

• ex. info from vestibular system, vision & kinesthetic integrated to give more complete sense of body’s orientation

selective attention

ability to focus on specific sensory input (we can tune stuff in and out)

inattentional blindness

failure to notice stimulus because attention is focused elsewhere

change blindness

situations where we fail to notice that background is changing because we’re focused on 1 element of scene

mind-wandering

attention is withdrawn from physical environment to focus on internal events

perception

selection, organization & interpretation of sensory input

illusion

misleading/misconnected perception

hallucination

perception with no basis in reality

synesthesia

perceptual phenomenon where stimulation of 1 sensory system creates perceptual experiences in another sensory system

• ex. hearing colours

perceptual constructions

mental model of external events

bottom-up processing

start with raw materials and put them together to complete perception

• ex. putting puzzle together without seeing image first

top-down processing

perception is guided by prior knowledge/expectations

• seeing a face and recognizing who it is

figure-ground organization

organizing a perception so that part of a stimulus appears to stand out as an object against less prominent background

shape constancy

perceived shape of object is unaffected by changes in retinal image

size constancy

perceived size of object remains constant despite changes in its retinal image

brightness constancy

brightness of objects remain same so long as they are illuminated by same amount of light

muller-lyer illusion

2 equal length lines tipped with inward/outward pointing vs appear to be of different lengths

depth perception

ability to see 3D space & judge distances accurately

depth cues

features of environment & messages from body that supply info about distance and space

binocular depth cues

perceptual features that impart info about distance and 3D space that requires 2 eyes

retinal disparity

difference between images projected onto each eye (eyes are 2.5 inches apart)

stereoscopic vision

perception of space & depth as result of each eye receiving different images (different images fused together)

convergence

degree to which eyes turn in to focus on a close object

pictorial depth cues

monocular depth cues found in paintings, drawings and photographs that impact info about space, depth & distance

monocular depth cues

perceptual features that impart info about distance and 3D space requiring just 1 eye

virtual reality

environments where sensory stimuli are provided by computer software to realistically simulate ‘real world’ events