chapter 4: sensation and perception

sensory adaptation

decreasing responsiveness to stimuli due to constant stimulation

sensory habituation

our perception of sensations is partially due to how focused we are on them

cock-tail party phenomenon

the ability to focus one's attention on a particular stimulus while filtering out a range of other stimuli

cornea

a protective covering and helps focus the light

pupil

when it’s opened or dilated by the iris, it lets more light in, and when it’s smaller, it lets less light in

iris

the muscles that control the pupil

accommodation

light that enters the pupil is focused by the lens

lens

is curved and flexible in order to focus the light

retina

acts as a screen on the back of your eye and contains specialized neurons that are activated by different wavelengths of light

transduction

refers to the translation of incoming stimuli into neural signals. not only does it apply to vision, but to all senses

cones

cells that are activated by color

rods

cells that are activated by black and white

fovea

an indentation at the very center of the retina that contains the highest concentration of cones

ganglion cells

the next layer of cells after bipolar cells

lateral geniculate nucleus

the axons of these cells make up the optic nerve that sends impulses to a specific region in the thalamus

blind spot

the spot where the optic nerve leaves the retina does not have any rods or cones

optic chiasm

the spot where the nerves cross each other

David Hubel and Torsten Wiesel

discovered that groups of neurons in the visual cortex respond to different types of visual images

trichromatic theory

the oldest and most simple theory that hypothesized that we have three types of cones in the retina: cones that detect the different colors blue, red, and green

afterimages

when you look at a color for a while and you look at a white background, these pop up

color blindness

individuals cannot see either red/green shades or blue/yellow shades, and in other cases, people can only see shades of gray

opponent-process theory

states that the sensory receptors arranged in the retina come in pairs; red/green pairs, yellow/blue pairs, and black/white pairs

amplitude

the height of the wave and determines the loudness of the sound, which is measured in decibels

frequency

refers to the length of the waves and determines pitch, measured in megahertz

eardrum

a thin membrane that vibrates as the sound waves hit it

hammer

eardrum is connected to this

anvil

hammer is connected to this

stirrup

anvil is connected to this

oval window

a membrane very similar to the eardrum and is attached to the cochlea

cochlea

a structure shaped like a snail’s shell filled with fluid

basilar membrane

the floor of the cochlea lined with hair cells connected to the organ of Corti

organ of Corti

neurons activated by the movement of the hair cells

place theory

holds that the hair cells in the cochlea respond to different frequencies of sound based on where they are located in the cochlea

conduction deafness

occurs when something goes wrong with the system of conducting the sound to the cochlea

nerve deafness

occurs when the hair cells in the cochlea are damaged, usually by loud noise

gate control theory

explains that some pain messages have a higher priority than others

papillae

the bumps you can see on your tongue

olfactory bulb

gathers the messages from the olfactory receptor cells and sends this information to the brain

limbic system

responsible for emotional impulses and memory

absolute threshold

the smallest amount of stimulus we can detect

subliminal

stimuli below our absolute threshold

difference threshold

the smallest amount of change needed in a stimulus before we can detect a change

Ernst Weber

found Weber’s law, which contained the finding of the difference threshold

signal detection theory

investigates the effects of the distractions and interference we experience while perceiving the world

false positive

when we think we perceive a stimulus that is not there

false negative

not perceiving a stimulus that is present

top-down processing

we perceive by filling in gaps in what we sense, occurs when you use your background knowledge to fill in gaps in what you perceive

schemata

mental representations of how we expect the world to be

perceptual set

a predisposition to perceive something in a certain way

backmasking

where there were supposed hidden messages musicians recorded backward in their music

bottom-up processing

the opposite of top-down processing. instead of using our experience to perceive an object, we use only the features of the object itself to build a complete perception

figure-ground relationship

asks the question of “what part of a visual image is the figure and what part is the ground or background?”

proximity

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

similarity

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

continuity

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

closure

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

constancy

our ability to maintain a constant

size constancy

objects closer to our eyes will produce images on our retinas, but we take distance into account in our estimations of size. we keep a constant size in mind for an object and know that it does not grow or shrink in size as it moves closer or farther away

shape constancy

objects viewed from different angles will produce different shapes on our retinas but we know the shape of an object remains constant. this depends on our familiarity with the usual shape of the object

brightness constancy

we perceive objects as being a constant color even as the light reflecting off the object changes

stroboscopic effect

images in a series of still pictures presented at a certain speed will appear to be moving

phi phenomenon

a series of lightbulbs turned on and off at a particular rate will appear to be one moving light

autokinetic effect

if a spot of light is projected steadily onto the same place on a wall of a dark room and people are asked to stare at it, they will say that it’s moving

visual cliff experiment

an infant is placed onto one side of a glass-topped table that creates the impression of a cliff, but the glass extends across the whole table, so the infant cannot fall

monocular cues

depth cues that do not depend on having two eyes

binocular cues

cues that depend on having two eyes

linear perspective

a type of perspective used by artists in which the relative size, shape, and position of objects are determined by drawn or imagined lines converging at a point on the horizon

relative size cue

if two objects are equal in size, one that is farther away will take up less of the field of view than the closer one

interposition cue

a type of monocular cue in which one object partially obscures or covers another object, giving the perception the object that is partially covered is farther away

texture gradient

the distortion in size which closer objects have compared to objects farther away

shadowing

by shading part of a picture, you can imply where the light source is and implies depth

binocular disparity

each of our eyes sees any object from a slightly different angle and the brain gets both images. it knows that if the object is far away, the images will be similar, but the closer it is, the more difference there will be

convergence

as an object gets close to our face, our eyes must move toward each other to keep focused on the object. the brain knows that the more the eyes converge, the closer the object must be

extrasensory perception

claiming to perceive a sensation outside the senses discussed in this chapter