sensation and perception comp check #2 (CH 5, 8, 10)

inverse projection problem

idea that a particular image on the retina could have been caused by an infinite number of different objects. This means that the retinal image does not unambiguously specify a stimulus 

viewpoint invariance

object properties dont change when viewed from different angles. responsible for the ability to recognize objects

perceptual organization

process by which small elements become perceptually grouped into larger objects

grouping

process by which visual events are put together into units or objects

segregation

process of separating one area/object from another

gestalt approach

the whole is different than a sum of its parts, perceptual illusions

structuralism

perceptions result from the summation of many elementary sensations

apparent movement

illusion of movement that occurs when 2 objects separated in space are presented rapidly, one after another, separated by a brief time interval

illusory contours

contour that is perceived even though it is not present in the physical stimulus

principle of pragnanz

of several geometrically possible organizations, the one that will actually be perceived is that one that possesses the simplest and most stable shape

figure

• thing-like

• in front, occludes part of background

• own the border or contour that distinguishes it from other items in the scene

background

extend spatially beyond the figure

gestalt approach to perception

the organization results from the fact that the brain and nervous system itself are highly organized

perception

result of the brain’s tendency to organize incoming stimulation patterns 

helmholtz’s unconscious inference

perception is a process of the brain making unconscious inferences or guesses based on cues provided by the proximal stimulus

bayesian inference

modern variant of helmhotz inference but put into mathematical form in terms of regularities

akinetopsia

when one cannot perceive motion

what does motion do

• resolve ambiguity

• provides contextual info

• draws attention

the reichardt detector

neural circuit which signals caused by movement of a stimulus across the receptors are processed by a delay unit and an output unit so that signals are generated by movement in one direction but not the opposite

delay unit

explains how neural firing occurs to different directions of movement. delays transmission of nerve impulses as they travel from the receptors towards the brain

output unit

compares signals from 2 or more neurons. vital for motion perception

image displacement signals

signals that there has been movement, the output unit only fires if signals from a & b arrive at the output unit at the same time

helmholtz’s corollary discharge theory

distinguishes 3 signals

• image displacement

• motor signals

• corollary discharge

induced motion

one object that is caused by the movement of another nearby object

motion aftereffects

illusion that occurs after a person views a moving stimulus and then sees movement in the opposite direction when viewing a stationary stimulus immediately afterwards

optic array

structured pattern of light created by the presence of objects, surfaces, and textures

globa optic flow

info for movement that occurs when elements in a scene move. the perceptions of global optic flow indicates that is it the observer that is moving and not the scene

corollary discharge signal

copy of the motor signal. movement will be perceived if the comparator receives just one signal (IDS or CDS). no movement is perceived if it receives both at the same time

CDS

eye follows moving stimulus

IDS

eye is stationary, stimulus is moving

IDS and CDS

eye moves across stationary scene

coherence

arrays of moving dots are used as stimulus. the degree of correlation between the direction of the moving dots (0% = all dots moving independently, 100% = all dots moving in same direction)

transcranial magnetic stimulation

presenting a strong magnetic field to the head that temporarily disrupts the functioning of a specific area of the brain

shortest path of constraint

apparent movement tends to occur along the shortest path between 2 stimuli

biological motion

self-produced motion of a person or living thing

implied motion

still picture depicts action that involves movement, so the observer could potentially extend the action depicted in the picture in the mind based on what will happen next

molyneux’s premise

we cant perceive depth by light, light arrives as the eye as points

oculomotor cues

muscular activation that changes shape of lens to focus on objects at various distances.

• the more strain in the lens required to focus image on retina, the closer the object is

convergence

muscular strain involved in making 2 eyes converge on a point of focus when we look at near objects

monocular (pictorial) cues

cues available with just one eye

interposition (occlusion)

given 2 objects, one that blocks the other is the one that is closest

perspective convergence/linear perspective

• converge: farther

• diverge: closer

motion parallax

objects appear to move in the opposite direction, things that are closer appear to move faster away from you while things farther away are moving slower

accretion and deletion

when texture goes out of view (deletion) or comes into view (accretion), provides info about depth depth. suggests it was behind something else

size constancy

maintaining a constant perception of depth or size despite differences in retinal image size

percept-percept coupling

we use one percept (distance) as a cue for another (size)

ponzo illusion

objects of the same size are perceived as different sizes because they are perceived to be at different distances

AMES room

sizes perceptually incorrect because they are perceived to be at the same distance

moon illusion

same object perceived different size because depth cues change