Perception Chapter 5

What is Perception?

Organization of information to make it useful

Psychophysical Approach Psychophysics – behavioral aspects of

a response to stimuli Difference threshold – degree of

change in a stimulus necessary for a person to detect the difference

Psychophysical Approach Signal-detection theory - sensitivity to stimuli

Physical condition Motivation Mood Attitude

Perceptual Constancies Our brain becomes a

storehouse of knowledge about details Size, shape and

color Memories play a role

in interpreting new stimuli

Four Constancies 1. Size 2. Shape 3. Brightness 4. Color

Perceptual OrganizationConstructionist

ViewThe brain

constructs a perception out of many individual sensations

Gestalt Psychologists Max Wertheimer Whole is more

important than the sum of the parts

Each part affects every other

Gestalt Laws of Perception 1. Law of Proximity – tendency to group

things together that are close to one another

Gestalt Laws of Perception 2. Law of Similarity – group things together

that have some visual element in common, such as size, shape, or color.

Gestalt Laws of Perception 3. Law of Continuation – tendency to see

interrupted lines as continuous lines

Gestalt Laws of Perception 4. Law of Closure – Tendency to fill in

missing details to complete a figure

Figure and Ground 3 Principles

1. The figure is more “thinglike” and more memorable than the ground

2. The figure is seen as being in front of the ground

3. The ground is seen as unformed material and seems to extend behind the figure

Bodily Depth Cues Monocular cues – one eye Binocular cues – two eyes 1. Accommodation – change in the shape of

the lens that varies with distance (1 eye) 2. Convergence – the way the eyes rotate

inward and outward with changes in distance (2 eyes)

3. Binocular disparity – difference between the images provided by each eye

Pictorial Depth Cues Monocular cues Give a two-

dimensional painting, photograph, or movie the illusion of depth where none exists.

Pictorial Depth Cues 1. Linear perspective – parallel lines appear

to converge as they move away from you 2. Relative size – objects that are known to

be the same size will convey depth if one is smaller than the other

3. Relative height – objects that are higher in a scene are usually perceived as being more distant

Pictorial Depth Cues 4. Overlap – a sensation of depth is created

when one object partially blocks another 5. Texture – changes in texture can convey

depth 6. Atmospheric (aerial)- distant objects tend

to look less sharp than close objects 7. Relative motion – objects that are close to

the car seem to be moving by quickly, while objects in the distance appear to move slowly

Perception of Motion Different kinds of movement:

A figure moving against a stationary background Objects at rest against a moving background Objects moving at different speeds in relation to

each other Observer’s own movements in relation to his/her

surroundings Induced movement

perception of movement of an object that is not moving

Illusions Muller-Lyer Illusion

Which line appears longer?

Illusions Ponzo Railroad Track

Illusion Which of the two horizontal

lines on the track appear longer?

IllusionsThe Necker Cube

The cubes seem to shift and another side seems closer to you.

Then it shifts back again

Illusions The Boring Figure

Designed by E.G. Boring

Ambiguous figure Young girl/old

woman

Illusions The Ames Room

Albert Ames Appears to be a normal

room Actually shaped so the

left corner is almost twice as far from the viewer as the right corner

The viewer perceives the nearer person as being much larger than the other, although both are exactly the same height

Illusions

What do you see?

Illusions