PSYCHOLOGY

Perceptual Organization

Perceptual Illusions

http://www.yorku.ca/eye/m-lillu.htm

Objectives

1. Understand how illusions help us understand perception

2. Understand perceptual organization principles

Outline A. Intro & illusions B. Organizational Principles

1. Form perception Figure/Ground Gestalt grouping

2. Depth perception Binocular cues - retinal dispartity,

convergence Monocular cues - 8

3. Motion Perception - stroboscopic, phi phenomemon

4. Perceptual Constancy - size & shape, size & distance, light, color

Perception

What can we learn from looking at the visual illusions #1-6 in your textbook?

Illusion reveal the ways we normally organize and interpret sensation.

Perceptual Illusions

Perceptual Organization: Muller-Lyer Illusion

Illusions

Muller-Lyer IllusionWe interpret the arrows as cues for

distance & length The arrows at the ends of the lines

make them appear of different lengths

Room Illusion

Room Illusion

Perceptual Organization: Size-Distance Relationship

Illusions

What assumptions do we make about rooms?

90 degree anglesSize & distance (we make the false

assumption that they are the same distance way)

To fool us they distorted the shape of the room

St. Louis Arch

Taller than wider?Wider than taller?

Perceptual Organization: Depth Perception

Relative Height

St. Louis Arch

Explanation: Relative Height - we perceive

objects higher in our field of vision as farther away

Perceptual Illusions

Illusions

Hans- Wallach’s - glowing blue wormGestalt principles grouping principles

lead you astray in this puzzleApply grouping principles like - continuity

Perceptual Illusions

Illusions

Hoffman - ripple illusion

It is a shading technique using light & shadows

Perceptual Illusions

Illusions

People tend to overestimate distance in the fog Light & Shadow issues Relative Clarity issues

Where can this information be useful in the real world?

Perceptual Illusions

Perception

What can we learn from looking at the visual illusions #1-6 in your textbook?

Illusion reveal the ways we normally organize and interpret sensation.

Which sense dominates?

Visual Capture tendency for vision to dominate

the other senses

Ex. - movie theater, roller coaster

Perceptual Organization: Gestalt

Our brains do more then just register info, we filter & infer to make sense

Gestalt = whole tendency to integrate pieces of

information into meaningful wholes

Necker Cube

The whole may exceed the sum of the parts

8 circles - people tend not to notice the circles but the whole box

Perceptual Organization: Illusory Contours

Fig. 15.2

Is there really a line down the middle?

Your eye perceives one

Outline M15 A. Intro & illusions B. Organizational Principles

1.Form perceptionFigure/GroundGestalt grouping

2.Depth perception Binocular cues - retinal dispartity,

convergence Monocular cues - 8

3.Motion Perception - stroboscopic, phi phenomemon

4.Perceptual Constancy - size & shap, size & distance, light

Form perception

Our brains do more then just register info, we filter & infer to make sense by discriminating what it is - form

We organize and interpret meaning

What is it?

Perceptual OrganizationForm perception

Figure and Ground--organization of the visual field into objects (figures) that stand out from their surroundings (ground); Reversible figures

What is it?

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What is it?

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Perceptual Organization: Gestalt

Grouping the perceptual tendency to organize

stimuli into coherent groups

Gestalt grouping prin.

Grouping Principlesa) proximity--group nearby figures togetherb) similarity--group figures that are similarc) continuity--perceive continuous patternsd) closure--fill in gapse) connectedness--spots, lines, and areas are

seen as unit when connected

Perceptual Organization: Grouping Principles

Perceptual Organization: Closure

Gestalt grouping principles are at work here.

Perceptual Organization: Grouping Principles

Gestalt grouping principles are at work here

Perceptual Organization: Grouping Principles

Impossible doghouse

Perceptual Organization:

Depth Perception ability to see objects in three

dimensions allows us to judge distance Somewhat innate ability as shown by

infants

Perceptual Organization: Depth Perception

Visual Cliff

Depth perception

1. Binocular cuesa) retinal disparity

images from the two eyes differ closer the object, the larger the

disparity(floating finger sausage)

b) convergenceneuromuscular cue - two eyes move inward for near objects

2. Monocular Cues

a) relative sizesmaller image is more distant

b) Interposition (overlay)closer objects blocks distant

object

Perceptual Organization: Depth Perception

Relative Size

Perceptual Organization: Depth Perception

Interposition

Monocular cues

c) relative clarityhazy object seen as more distant

d) texture coarse --> closefine --> distant

Perceptual Illusions

Monocular cues

e) relative heighthigher objects seen as more

distant

Perceptual Organization: Depth Perception

Relative Height

Monocular cues

f) relative motioncloser objects seem to move faster

g) linear perspectiveparallel lines converge with distance

h) relative brightnesscloser objects appear brighter

Perceptual Organization: Depth Perception

Light and Shadow

Perceptual Organization: Depth Perception

Perspective Techniques

Perceptual Organization: Depth Perception

Illusory Depth

Perceptual Organization: Depth Perception

Illusory Depth Explanation

Motion Perception

1. Stroboscopic movement - still pictures can be perceived as moving ( cartoons & film)

2. Phi phenomenon - 2 adjacent stationary lights blink on/off in succession are perceived as moving

Perceptual Constancy Perceptual Constancy

perceiving objects as unchanging even as illumination and retinal image change color shape size

Size & distance p.239

Monster & Ponzo illusions

Monster - linear perspective, relative height; cues to distance & size

Ponzo - we perceive the bar as farther away as being larger based on experience

Moon illusion

Moon looks larger at the horizon then it does high in the sky

Explanation: cues to objects distances at the horizon make the moon seem farther away

Similar to the monster & ponzo illusion

Perceptual Organization-Brightness Contrast

Perceptional Constancy

1. Shape2. Size & distance3. Color4. Lightness/Brightness

Concentrate on the 4 dots in the middle for 30 sec.

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Which is line is longer?

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