Visual Imagination

Perception

What is perception? Perception is a process by which the brain

codifies and organizes sensory impulses.

Perception is important because people’s thoughts and ultimately behavior is based on their ability to sort out sensory information.

Why is perception important?

Visual Perception deals with:

the mechanics of observation the discrimination of color the discrimination of shapes of things the discrimination of patterns the discrimination of scale and dimension

of things the discrimination of distance between

objects the discrimination of background and foreground the discrimination of depth of field

PERCEPTION is the process of identifying the sensory input, and categorizing it accordingly.

As a process, perception tends to function similarly among human beings. This does not mean, however, that all people observing the same thing are perceiving the same thing.

Perception can be strikingly different from person to person depending on multiple factors such as:

1. Quality and efficiency of the vision apparatus (color blindness, etc.)

2. Social and cultural adaptation (perspective and geometry)

LEFT - 20 th Century artist Louis Wein. Portraits of his cat over a period of time that he developed schizophrenia.

ABOVE Photo taken while hallucinating.

3. Chemical influences on the cerebral cortex. (Ex. use of mind altering drugs)

4. Personality characteristics of the observer.

A. Motivation - perceiving what we want to perceive.

B. Expectation - perceiving what we ought to perceive

Pursuit movements: following a moving object within a visual field. Hunters (skeet shooters) and athletes have more developed observation skills in this regard.

5. Methods of observation

To grasp and identify visual impulses the eye reliesheavily on methods of observation such as:

Observe the path the jet ofwater takes from its originto the end of the arc.

During reading the eyes pause briefly on individual words or sets of words. The eye moves between fixations at a rate of 20 to 30 msecs (seccades). Notice that the eye stops are not always sequential.

Seccades: short scanning movements used in casual or directed observation.

The recording on the right shows the scan-path of the bust on the left over a period of three minutes.

The drawings on the right provide the subject matter that is scanned by two different observers on the left. Notice how each scans the drawings differently.

Drawing Observer A Observer B

Scan-path showing how an individual will perceive the same subject matter differently if scanning for different things.

1 - looking at composition3 - looking for age5 - looking for dress7 - looking for relationships

6. Observation within different contexts

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Scientists, psychologists in particular, have attempted to discover how the human visual system perceives and grasps entities. One of the earliest and intuitively most acceptable theories about perception was proposed by Wertheimer in 1923, and later elaborated by Koffka in 1935. These Gestaltists formulated the principles or “laws” of grouping or patterning.

Figure vs. Ground

One of the fundamental issues invisual perception concerns how we look at a scene or an image and determine what is the object of interest – figure, and what is ground the context the figure occurs in - ground.

Edges and contours are usuallycritical in this respect and will often provide good information

Similarity

Similar objects are seen as independent entities.

When elements are arranged in groups that define an object, we tend to see the object and not the elements.

Proximity

Proximity

The cluster has a separate identity outside the organized group.

The tendency to perceive unseen parts of a patterns as continuing in a predictable and simple manner.

Continuity

ClosureAn object may be partly occluded by other objects in our environment. The visual system fills in the missing information

ClosureThe mind has an uncanny ability to imagine shapes where there are none

Symmetry: regions bounded by symmetrical borders tend to be perceived as coherent figures

Continuity and Closure

What does the sign say?

Visually perceived images that move towardeach other are seen as forming a common object.

This principle is best imagined in terms of those animals you see on nature shows that seem to perfectly blend into their background, until they move. Then suddenly theyappear visible.

Common Fate

Common Fate

Common Fate

Common Fate

Common Fate

Simplicity

We tend to impose the simplest, best fitting, interpretation to any stimulus.

In the imageon the left, we tend to reduce the figures to the simplest shapes.