1. Unit VI: Perception: Perceptual constancy
Stimuli changes, object perceived to stay the same
In other words:
Image on retina changes, but brain perceives image as being constant/unchanging
Stimuli changes, but percept remains the same
Sensation changes, perception doesn’t

2. Unit VI: Perception: Perceptual constancy
Changes include:
Shape
Size
Level of illumination (light)
Color
Distance

3. Unit VI: Perception: Perceptual constancy
Shape constancy
For familiar object; image on retina changes, still perceive it as original shape
Image on retina changes because object moved in some way

4. Unit VI: Perception: Perceptual constancy
Size constancy
Objects perceived as having constant size, even when distance varies
Size constancy: the brain perceives the two people as being the same size, because they’re both people.

5. Unit VI: Perception: Perceptual constancy
Lightness/brightness constancy
Object perceives to have constant color even when illumination varies
Relative luminance: Amount of light an object reflects relative to its surrounding

6. Unit VI: Perception: Perceptual constancy
Lightness/brightness constancy
Example
Black and white sheets of paper in normal light
Looks black and white
Black and white sheets of paper in high light
Both still appear black and white
Both are reflecting back more light than previously

7. Unit V: Sensation – Color vision
Color vision – theories
Color constancy
How we see color is influenced by its surroundings & context
Put object into different surrounding, color may appear different
Inner squares all the same color gray?

8. Unit VI: Perception: Perceptual constancy
Lightness/Brightness Constancy vs. Color Constancy
Lightness/brightness constancy:
Level of light changes
Image on retina different
Colors perceived the same
Color constancy:
Surroundings change
Image on retina the same
Color perceived differently

9. Unit VI: Perception: Perceptual constancy
Illusions - Perceptual Constancy & Monocular Cues
Constancy:
image on retina different
brain perceives images as unchanging
Most cues:
images on retina different
brain perceives images as different

10. Unit VI: Perception: Perceptual interpretation
Is our perception learned or are we born with it?
Experiments show - both
Colin Blakemore
Graham Cooper
Cambridge

11. Unit VI: Perception: Perceptual interpretation
Is our perception learned or are we born with it?
Kittens – blinders from birth until six months (critical period):
Visual cortex didn’t develop
Eye works properly – transducts, etc.
Visual cortex can’t process

12. Unit VI: Perception: Perceptual interpretation
Is our perception learned or are we born with it?
Kittens – blinders from six months until year old:
Little effect
Period of adaptation; no permanent effect

13. Unit VI: Perception: Perceptual interpretation
Is our perception learned or are we born with it?
Kittens – blinders from birth until six months: one eye
Little effect
Period of adaptation; no permanent effect

14. Unit VI: Perception: Perceptual interpretation
Is our perception learned or are we born with it?
Kittens – environment with vertical lines (critical period)
Feature detection - horizontal lines don’t develop

15. Unit VI: Perception: Perceptual interpretation
Perceptual adaptation
Ability to adapt to changed visual input
Example:
New glasses
Glasses - images upside down
Glasses - images left to right
Period of adaptation

16. Unit VI: Perception: Perceptual interpretation
Perception and the Human Factor
Human factors psychology
Help design appliances machines, settings, etc. that fit our natural perceptions
Explores how :
people and machines interact
machines/technology can be adapted to human behaviors
“User friendly”

17. Unit VI: Perception: Perceptual set/mental disposition
Mental predisposition to perceive things a certain way
Varies, person-to-person
Based on several factors

18. Unit VI: Perception: Perceptual set/mental disposition
Do not step on
on the grass
Perceptual set/mental disposition
1) Schema
Assimilation
2) Context
3) Anticipation
We see what we expect to see
acoindrcg to an Eslnigh usintreviy sdtuy the oerdr of ltteers in a word donset mettar the only tnhig ttahs imtorpnat is that the fsirt and last letetr of every word is in the crrocet potsoiin The rset can be jlembud and one is sltil albe to read the txet wuohtit dilffcutiy

19. Unit VI: Perception: Perceptual constancy
Illusions - Perceptual Constancy & Monocular Cues
With many illusions: combination of cues & constancy trick the brain
I.e. images on retina is same, but brain perceives them differently because of cues

20. Unit VI: Perception: Perceptual constancy
Illusions - Perceptual Constancy & Monocular Cues
Shepard’s table
Same images on retina; brain perceives them differently
Relative height

21. Unit VI: Perception: Perceptual constancy
Illusions - Perceptual Constancy & Monocular Cues
Ponzo Illusion & Shepard’s Monsters
Both images same size (same image on our retinas)
Linear perspective & relative height: second monster/bar should be further away
So should be smaller (relative size)
But it’s not, so brain perceives it as larger (size constancy)

22. Unit VI: Perception: Perceptual constancy
Illusions - Perceptual Constancy & Monocular Cues
Moon illusion
Moon close to horizon appears larger
Shrinks as it rises
Variant of Ponzo Illusion
Relative height + relative size