sensation and perception exam 2

trichromacy

detection, three cone class (red, green, blue), caused by wavelength sensitivity

Dunbar’s number

size of social group you usually associate with

illuminance

light source

luminance

light hitting your eye (illuminance x reflexivity)

three steps to color perception

detection, discrimination, appearance

color detection

scotopic (rods) and photopic (cones)

S cone

blue light (~400nm)

M cone

green light (~550nm)

L cone

red light (~650nm)

rod nm sensitivity

~500 nm

additive color mixing

red, green, blue

subtractive color mixing

cyan, magenta, yellow; remainder of material that isn’t absorbed is perceived

RGB color space

outputs of long, medium, and short wavelengths

illegal color combos

reddish-green, bluish-yellow

single opponent cell

in V1; on center, off surround of opposing color

opposing color combos

red/green, blue/yelllow, black/white

double opponent cell

in cortex; on and off center, on and off surrounding, prefers bars

protanope

lack L cones

Deuteranope

lack of M cones

Trianope

lack of S cones

color anomalous

two cones (L and M cones) are so similar you can’t really make discriminations

cone monochrome

truly color blind, only one cone

rod monochromat

only rods

albinism

few rods

tetrachromats

extra cone class- orange, 12% of women

binocular vision

two eye vision, humans ~120 visual field

binocular disparity

differences in 2 retinal images of the same scene

stereopsis

ability to percieve depth by using both eyes

depth cue

info about 3D image

monocular depth cue

available when world is viewed with 1 eye, inference

binocular depth cue

relies on info from both eyes, comparison of 2 images in cortex

blue tint

atmosphere filters out red/green light first

motion parallax

how things move relative to your position

convergence

ability of two eyes to turn inward to focus on near object

divergence

ability of two eyes to turn outward to focus on far objects

corresponding retinal points

points in retina of each eye of a single object formed at same distance from fovea in each eye

vieth-müeller circle (horopter)

location of objects whose images fall on geometrically corresponding points in the two retinas

attention

selective processes, impossible to handle all inputs at once

external attention

attending to stimuli outside of yourself

internal attention

attending to one line of thought over another

overt attention

directing sense organ toward stimuli, ex, turn head or eyes

covert attention

attending to stimuli without outward sign you’re doing so, select parts of visual scene to focus on

eye movement

gives away where you’re looking

fixations

white blobs, part of the conscious experience

saccades

long jumps between fixations, supressed info

divided attention

split between 2 different stimuli, can improve your ability (Cornell study)

spotlight model

areas that recieve extra processing in fovea

salience

vividness of stimuli relative to neighbors

serial search

looking for one object makes it stand out more

parallel search

looking for multiple objects, makes finding them more difficult

crowding

more difficult to see an object if there are other things around it

contrast effects

things pop out more with higher contrast, light blue hard to see

faces

more symmetrical= easier to identify

spot it game

size constancy, orientation, symmetry

visual search

time to identify an item, slower with each added item

search slope

measured in milliseconds, provides information about how difficult the task is

feature search

one object, one distractor

conjunction search

one object, multiple distractors

spatial configuration search

find multiple things, multiple distractors

attentional blink

brain takes a break after identifying target stimili, ex can’t remember letter after X in flash of letters

object based attention

brain focuses on objects not just empty space

neglect

inability to respond to stimuli in visual field, damage to right parietal lobe=inability to see left field

extinction

mild form of neglect, can only see one object in visual field

stimultanagnosia

can identify one object in visual field, cannot tell a story with the image

Balint Syndrome

inability to localize in space, includes stimultanagnosia

change blindness

we aren’t coding as many details as we think, ex. cornell study swap person

inattentional blindness

if we don’t pay attention to something, its as if we didn’t even see it

middle temporal lobe (MT)

where retinal images are fused together

motion after-effect (MAE)

caused by release of inhibition of cells next to firing cells for one direction

Akinetopsia

motion blindness, can see faces, acuity, color, stereo; can’t see things move

efferent copy/ corollary discharge

eye movement control area of brain tell other parts of brain where eyes are heading to next

vestibulo-ocular reflex

involuntary, eyes focused on target even if body moves unexpectedly

optokinetic nystagmus (OKN)

ex. watching a train, eyes jump from car to car

microsaccades

always present, side-to-side, up-and-down

frontal eye field

tells muscles where to direct eye next, connected to V1 and superior colliculus, FEF

smooth pursuit

following a moving object, voluntary

peripheral drift illusion

in periphery, not dependent on color, specific dark and light patterns, moving snakes illusion

metamers

different mixtures of wavelengths that look identical to a human

opponency

discrimination, in ganglion cells, LGN, and V4, caused by combos of different wavelengths

V1 fMRI response

relies on percieved size, not retinal size

binocular rivalry

competition for two eyes to control perception ex. different stimuli presented in the two eyes

strabismus

misalignment of eyes from birth, problems in ocular muscle development

real world visual search

easier to find things if we know the context, ex. mug should be on counter

constancy

appearance, in cortex, cause lighting and scene geometry