Dr.safeyya Adeeb Alchalabi Perception Dr.safeyya Adeeb Alchalabi

Perception Is the method by which the brain takes all the sensations a person experiences at any given moment and allows them to be interpreted in some meaningful fashion.

constancies Perceptual constancy: Something that remains the same, the property of remaining stable and unchanging.

Perceptual constancy Size constancy The tendency to interpret an object as always being the same size, regardless of its distance from the viewer (or the size of the image it casts on the retina).

Perceptual constancy Shape constancy Is the tendency to interpret the shape of an object as constant, even when changes on the retina.

Perceptual constancy Brightness constancy The tendency to perceive the apparent brightness of an object as the same even when the light conditions change.

Gestalt principles The tendency to group objects and perceive whole shapes.

Gestalt psychology Back to Germany, by the psychologist Max Wertheirmer. Wertheirmer believed that psychological event such as perceiving and sensing could not broken down in to any smaller elements and still be properly understood, so perception can only be understood as whole, entire event. “The whole is greater than the sum of its parts” Wertheirmer and others believed that people naturally seek out patterns (“whole”) in the sensory information available to them.

Gestalt psychology Wertheimer and others devoted their efforts to studying sensation and perception in their new perspective, Gestalt psychology. (Gesh-TALT) is a German word meaning “an organized whole” or “configuration”, which fit well with the focus on studying whole patterns rather than small pieces of them.

Gestalt psychology Today, Gestalt ideas are part of the study of cognitive psychology, a field focusing not only on perception but also on learning, memory, thought processes, and problem solving. The Gestalt approach has also been influential in psychological therapy, becoming the basis for a therapeutic technique called Gestalt therapy.

Gestalt principles

Gestalt principles Figure-ground relationships Refer to the tendency to perceive objects or figures as existing on a background. Organization depends what we see as figure (object) and what we perceive a ground (context).

Figure-ground relationships

In which the figure and the ground seem to switch back and forth. Reversible figures In which the figure and the ground seem to switch back and forth.

Figure-ground relationships People seem to have a preference for picking out figures from background even as early as birth.

Gestalt principles of grouping Proximity (nearness) Another very simple rule of perception is the tendency to perceive objects that are close to one another (in space or time) as part of the same grouping (or belong together).

Gestalt principles of grouping Similarity Refers to the tendency to perceive things that look similar as being part of the same group. (Objects that have similar characteristics are perceived as a unit).

Gestalt principles of grouping Closure is the tendency to complete figures that are incomplete. (we perceive figures with gaps in them to be complete).

Gestalt principles of grouping Continuity It refers to the tendency to perceive things as simply as possible with continuous pattern rather than with a complex, broken-up pattern. (we tend to perceive figures or objects as belonging together if they appear to form a continuous pattern).

Gestalt principles of grouping Common region The tendency is to perceive objects that are in a common area or region as being in a group.

Depth perception The capability to see the world in three dimensions. It seems to develop very early in infancy, if it is not actually present at birth.

Depth perception

Perceptual illusion A false perception of actual stimuli involving a misperception of size, shape, or the relationship of on element to another.

Perceptual illusion

Feature detectors They respond to specific features of a stimulus. Simple cells Neurons in the primary visual cortex that respond best to bars of light of a specific orientation. Complex cells which respond to orientation and movement. End-stopped cells which respond best to corners, curvature, or sudden edges.

Muller-Lyer illusion

Moon illusion

Perceptual set (perceptual expectancy)

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