BV7 - distance perception

What constancies do we assume (carried out by cortical processes)?

1. shape constancy

2. size constancy

3. color constancy

4. lightness constancy

What are the components of spatial localization?

1. distance perception

2. direction perception

What are the components of distance perception?

relative: distance between objects (depth)

absolute: distance from body (egocenter)

what are the components of direction perception?

1. oculocentric

2. egocentric

Where is relative distance perception good?

only at short distances

Is absolute distance perception good or bad?

bad!

why does the sun, moon and stars appear equidistant?

at further distances we underestimate how far that distance is → not as accurate as close distances

Do size and distance perception interact?

yes

What is Emmert's law?

the relationship of perceived size and perceived distance

perceptual law

What is the law of visual angle?

a physical law that states the relationship between visual angle to physical size and physical distance

further distance → smaller angular size

closer distance → larger angular size

what is linear perspective based on?

relationship between angular size and distance

What is size constancy?

ability to perceive the correct size of an object despite changes in its retinal image size

Are oculomotor cues (convergence, accommodation) to distance good or bad?

bad

What is overlay?

nearer objects occlude more distant ones

How do we interpret shadows?

as if light were coming from above → relative depth is cued by the position of highlights and shadows on objects

What is aerial perspective?

blue haze obscures more distant objects because of atmospheric scatter → more distant objects are less distinct

How tall is an object that extended from the ground to the horizon?

1 eye-height tall (h) regardless of distance

How does the angle subtended from the horizon relate to the distance of objectin a picture?

distance of objects is inversely related to the angle subtended from the horizon

therefore, size can be estimated by the angle objects subtend relative to the ground horizon distance

What is linear perspective?

relative sizes of retinal images provide information about the relative distance of objects

ex: a pencil half the size of another will look twice as far away

What assumptions do we make about object size?

similar looking objects are assumed to have identical sizes → telephone poles, fence posts

continuous objects are assumed to be unchanging in size → roads, railroad tracks

familiar object are assumed to be their expected size → coins, ruler illusion

why does distance/size perception change as overall distance changes, despite distance between two objects being the same?

difference in station point (distance of first object) d/t picture only conveying relative distance info

What happens if you overestimate the station point?

the separation between objects will be expanded

What happens if you underestimate the station point?

separation of objects will be foreshortened

How does foreshortened depth affect the speed?

slows apparent speed of objects moving toward or away from observer

Portraits taken closer than expected will be perceived as?

birdlike because of expanded perceived depth due to overestimated distance

What motion cue do we use to see depth?

motion parallax

What is motion parallax?

movement of body causes differential retinal image motion of objets at different distances

what is motion determined by?

direction of motion of the body relative to the scene

what is tangential motion?

moving horizontally tangentially to the scene

what is radial motion?

moving horizontally toward the scene

How does motion parallax cue depth?

objects closer to us move faster than objects farther from us

What is the focus of expansion?

image velocity is zero for the point toward which the body is moving → aka radial motion toward a near point

images of objects that are farther than the focus of expansion have what type of motion?

with

images of objects that are nearer than the focus of expansion have what type of motion?

against