Perceptual Organization PSYCHOLOGY Perceptual Organization

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

Objectives Understand how illusions help us understand perception Understand perceptual organization principles

Outline A. Intro & illusions B. Organizational Principles Form perception Figure/Ground Gestalt grouping Depth perception Binocular cues - retinal dispartity, convergence Monocular cues - 8 Motion Perception - stroboscopic, phi phenomemon 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 Illusion We 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 angles Size & 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 worm Gestalt principles grouping principles lead you astray in this puzzle Apply 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 Form perception Figure/Ground Gestalt grouping Depth perception Binocular cues - retinal dispartity, convergence Monocular cues - 8 Motion Perception - stroboscopic, phi phenomemon 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 Organization Form perception Figure and Ground--organization of the visual field into objects (figures) that stand out from their surroundings (ground); Reversible figures

What is it?

What is it?

Perceptual Organization: Gestalt Grouping the perceptual tendency to organize stimuli into coherent groups

Gestalt grouping prin. Grouping Principles proximity--group nearby figures together similarity--group figures that are similar continuity--perceive continuous patterns closure--fill in gaps 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 cues retinal disparity images from the two eyes differ closer the object, the larger the disparity (floating finger sausage) convergence neuromuscular cue - two eyes move inward for near objects

2. Monocular Cues relative size smaller 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 clarity hazy object seen as more distant d) texture coarse --> close fine --> distant

Perceptual Illusions

Monocular cues e) relative height higher objects seen as more distant

Perceptual Organization: Depth Perception Relative Height

Monocular cues f) relative motion g) linear perspective closer objects seem to move faster g) linear perspective parallel lines converge with distance h) relative brightness closer 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 Stroboscopic movement - still pictures can be perceived as moving ( cartoons & film) 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 Shape Size & distance Color Lightness/Brightness

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

Which is line is longer?