Unit 4: Sensation & Perception Module 16: Perceptual Organization

Perceptual Illusions Illusions reveal the ways we normally organize and interpret our sensations. Visual Capture – the tendency for vision to dominate the other senses. When vision competes with other senses, it usually wins.

Ames Room Invented by ophthalmologist Adelbert Ames, Jr. in 1934. The Ames room was designed to manipulate distance cues to make two same-sized girls appear very different in size. Click to reveal bullets and to show explanation.

Organizational Principles Gestalt – organizing pieces into a meaningful “whole”. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes. We take information and infer perceptions in ways that make sense to us.

Figure and Ground Perception Figure – Object Ground – Surroundings Figure-Ground – the organization of the visual field into objects that stand out from their surroundings. Goblet or two faces? Stepping man, or arrows?

Grouping Proximity – Group nearby figures together. We don’t see 6 separate lines, but 3 sets of two lines. Similarity – We group together figures that are similar to each other. We see triangle and circles as vertical columns, not horizontal shapes.

Grouping Continuity – We see smooth, continuous patterns. Two lines or semicircles? Connectedness – We see the two dots and the line as a single unit. Closure – We fill in the gaps to create a complete, whole object. Triangles?

This is a painting on the sidewalk. Depth Perception Depth Perception – Seeing two dimensional objects as three dimensional. Allows us to estimate distance. This is a painting on the sidewalk.

Depth Perception Visual Cliff – test of depth perception in babies. Babies develop this ability at crawling age.

Binocular Cues Binocular Cues – depth cues that depend on the use of two eyes. Retinal disparity – the slightly different view the two eyes have of the same object because the eyes are a few centimeters apart. The degree of retinal disparity decreases with distance. With both eyes open, your brain fuses the two images, resulting in perception of depth.

Binocular Cues Convergence – the inward turning of the eyes that occurs when you look at an object that is close to you. The closer the object, the more convergence. Look at your nose. Your eyes converge inward.

Monocular Cues Monocular Cues – depth cues using either eye alone. Relative Size – The closer of two same size objects casts a larger image on your retina than the farther one. Bigger canoe is closer.

Triangle is closer because it blocks the circle and square. Monocular Cues Interposition – one object partially blocks our view of another, we see it as closer. Triangle is closer because it blocks the circle and square.

Hazy, cloudy forest is farther away than clear, sharp trees. Monocular Cues Relative Clarity – closer objects appear sharper than more distant, hazy objects. Hazy, cloudy forest is farther away than clear, sharp trees.

Circles look closer, while densely packed areas seem farther away. Monocular Cues Texture Gradient – closer objects have a coarser, more distant texture than far away objects that appear more densely packed or smooth. Circles look closer, while densely packed areas seem farther away.

Monocular Cues Relative Height – The lowest objects in our field of vision seem the closest. Images higher in the picture seem farther away. Night? Ground Figure

Nearby objects pass quickly while far away objects appear stationary. Monocular Cues Relative Motion (Motion Parallax) – As we move, objects that are actually stable appear to move. Nearby objects pass quickly while far away objects appear stationary.

The tracks seem to meet in the distance. Monocular Cues Linear Perspective – Parallel lines seem to converge in the distance. The tracks seem to meet in the distance. 1 point perspective

Seems closer because it reflects more light. Monocular Cues Light and Shadow (Relative Brightness) – Closer of two identical objects reflects more light to your eyes. Seems closer because it reflects more light.

Motion Perception Phi Phenomenon – the illusion of motion created by presenting visual stimuli in rapid succession. Flipbook video!

Shape and Size Constancies Shape Constancy – an object appears to maintain its normal shape regardless of the angle from which it is viewed.

Shape and Size Constancies Size Constancy – an object appears to stay the same size despite changes in the size of the image as it moves farther away or closer.

Shape and Size Constancies Size-Distance Relationship – Farther objects seems larger.

Lightness Constancy Brightness Constancy – an object maintains a particular level of brightness regardless of the amount of light reflected from it. However, when the context changes, the perceived brightness or color can also change. Remember A & B are the same color, but we perceive B as lighter because of the surrounding context.