1. Chapter 6: Perception

2. Perception – the awareness, integration, and organization of sensory stimuli
Bottom-up processing – organization of information without the use of prior knowledge – beginning with the individual elements that are structured together to form a whole
Each part is given attention and not until individual elements are connected is the whole recognized or identified.
Putting together a puzzle by looking at how the pieces fit together
Top-down processing – organization of information that uses prior knowledge to form the whole
The final whole is already known and then the individual elements are identified
Putting together a puzzle by looking at the picture on the box

3. Selective Attention- Focusing of conscious awareness on a particular stimulus
Cocktail Party Effect- The ability to attend selectively to only one voice among many
Inattentional Blindness - When people show a lack of awareness of happenings in their visual environment
Change Blindness
Change Deafness
Choice Blindness

4. Perceptual Organization
Gestalt Psychology- group of German psychologists interested in how the mind organizes sensations into perceptions
Gestalt – When given a cluster of sensations, we tend to organize them into a gestalt – a “form” or a “whole”
“In perception, the whole may exceed the sum of its parts”
Gestalt Principles:
Figure-ground - Ability to distinguish between the figure as the foreground and the ground as the background

5. Gestalt Principles cont.
Grouping – Our mind follows certain rules for grouping stimuli together
Proximity – Tendency to perceive objects that are close together as belonging together
Similarity – Tendency to group similar objects together to make a whole
Continuity – Tendency to see an object continuing despite an obvious break
Connectedness – Tendency to see objects that are uniform and linked as one unit
Closure - Tendency to fill in the gaps to complete a whole object

6. Depth Perception
Biology predisposes our sense of height; experience amplifies it.
Depth Perception (seeing objects in 3 dimensions)
Visual Cliff Experiment-Eleanor Gibson & Richard Walk designed experiment prove depth perception is innate

7. Depth Perception – Binocular Cues
Depend on both eyes (depth cues)
Retinal disparity – by comparing images from two eyes, the brain computes the difference, the greater the distance between the two images, the closer the object
3-D movies rely on retinal disparity
Convergence - muscles rotate inward when viewing an object nearby; the greater the inward strain, the closer the object

8. Depth Perception – Monocular Cues
Relative Size - Objects which appear to be smaller, we view as farther away and larger objects are closer

9. Depth Perception – Monocular Cues
Interposition (overlap) - when objects block or otherwise obscure our view of other objects, we perceive obscured object as farther away

10. Depth Perception – Monocular Cues
Relative Clarity - Objects further away appear blurry or hazy - caused by atmosphere

11. Depth Perception – Monocular Cues
Texture Gradient- The coarseness or smoothness of an object is used as a cue for distance. Objects far away appear smaller and more densely packed.

12. Depth Perception - Monocular Cues
Relative Size: If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away.

13. Depth Perception – Monocular Cues
Motion Parallax (Relative Motion) - When moving, farther objects move slower.

14. Depth Perception - Monocular Cues
Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance.

15. Depth Perception – Monocular Cues
Light and Shadow: Nearby objects reflect more light into our eyes than more distant objects. Given two identical objects, the dimmer one appears to be farther away.
From “Perceiving Shape From Shading” by Vilayaur
S. Ramachandran. © 1988 by Scientific American, Inc.
All rights reserved.