S+P Unit 2: Perceptual Constancy

perceptual constancy

some object properties remain constant even though proximal stimulus conditions change

1. registration/sensation
2. apprehension/perceptual adjustment

2 phases of perceptual constancy

size constancy

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

constancy scaling

we are constantly adjusting based on what we know

minification

when we adjust, result is a bit of an understatement, not a perfect process

direct perception/ecological explanation to size constancy

we compare objects to context/background which helps us adjust

constructive explanation to size constancy

experience plays a role

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 (constructivists say it's because of wall corners)

Ponzo illusion

An illusion of size in which two objects of equal size that are positioned between two converging lines appear to be different in size. Also called the railroad track illusion.

moon illusion

An illusion in which the moon appears to be larger when it is on or near the horizon than when it is high in the sky.

shape constancy

the perceived shape of an object remains constant, despite changes in its retinal image

normative orientation

based on our own experience with an object

box alignment illusion

parallel line objects appear to be moving different ways, sensitivity to instructions (look at line vs which way are objects moving)

lightness/whiteness constancy

the perceived lightness of an object remains constant, despite changes in its retinal image

ratio principle

the ratio of luminance between an object and surrounding elements determines the object's perceived lightness (direct/computational theory)

retinex theory

ratio principles may only work on localized edges of objects, related to lateral inhibition (direct/computational theory)

Cues about Illumination

depends on reflectance levels

Gelb 1929 demonstration

white/black disc, ratio principle restored once projector was revealed, shows experience element

color/hue constancy

the perceived color of an object remains constant, despite changes in its retinal image

cues and knowledge (disc experiment)

constructive explanation for color constancy

ratio principle

direct/computational explanation for color constancy

adaptation

physiological explanation for color constancy

position constancy

the perceived position of an object remains constant, despite changes in its retinal image

object-relative position

The position of one object in relation to the position and orientation of another object

Egocentric Direction

direction in which the object is located relative to yourself

-loudness (related to intensity)
-odor (nose-blind)

what other modalities does constancy happen in