The document discusses visual perception and how the brain processes visual information. It explains that perception is the process by which sensory impulses are organized and coded by the brain. Visual perception involves discriminating various visual attributes like color, shape, distance. It describes how visual impulses travel from the retina to the brain areas involved in visual processing and interpretation. Key areas mentioned are the optic chiasm, lateral geniculate nucleus, and primary visual cortex. The document also discusses factors that can influence perception like quality of vision, culture, drugs, personality, and observation methods. Finally, it introduces Gestalt principles of visual organization like figure-ground, similarity, proximity, continuity, closure, and simplicity.

1. Visual Imagination

2. Perception
What is perception?
 Perception is a process by which the brain
codifies and organizes sensory impulses.
Why is perception important?
 Perception is important because people’s
thoughts and ultimately behavior is based
on their ability to sort out sensory
information.

3. 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

4. When visual impulses leave the retina through the
optic nerve, they cross over to their respective
areas in the brain, from which they will be
interpreted. The crossover are is called the optic
chiasm.

5. From the optic chiasm the impulses continue their
travel through the optic tract to the lateral geniculate
nucleus, a clearing house, where superfluous visual
information is discarded.

6. From the lateral geniculate nucleus, the impulses
radiate to the primary visual cortex of the
occipital lobe.

7. The Primary Visual Cortex is made up of a large
number of “modules” that contain a large number of
nerve cells that correspond to different aspects of the
retina.

8. The retina is not evenly represented but, instead,
more primary cortex is devoted to images at or near
the fovea.
Some nerve cells in a module respond only to lines
of certain orientations, others respond only to
motion, others to color, etc.
The function of the primary cortex it to codify the
basic features of the images it receives.

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

10. As a process perception tends to be similar among
human beings. This does not mean, however, that all
people observing the same thing perceive 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.)

11. 2. Social and cultural adaptation (perspective and
geometry)

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

13. 4. Personality characteristics of the observer.
A. Motivation - perceiving what we want to
perceive.
B. Expectation - perceiving what we ought to
perceive

14. 5. Methods of observation
To grasp and identify visual impulses the eye relies
heavily on methods of observation such as:
Pursuit movements: following a moving object
within a visual field. Hunters (skeet shooters) and
athletes have more developed observation skills in
this regard.
Observe the path the jet of
water takes from its origin
to the end of the arc.

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

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

17. 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

18. Scan-path showing
how an individual will
perceive the same
subject matter
differently if scanning
for different things.
1 - looking at composition
3 - looking for age
5 - looking for dress
7 - looking for relationships

19. 6. Observation within different contexts

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21. 7. Observation patterns - Gestalt
The next segment will deal with these in greater
depth.

22. 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.

23. Gestalt is a German word that means: a
whole entity or entirety.

24. We see everything
f or the f irst time. .
We see everything for the first time.

25. Gestalt theory claims that problem solving is
productive and reproductive.
Reproductive problem solving draws on previous
experiences whereas productive problem solving
involves insight and restructuring of the problem.
Reproductive problem solving could be a hindrance
to finding a solution, since a person may fixate on the
known aspects of a problem and so be unable to see
novel interpretations that might lead to a solution.

26. GESTALT PRINCIPLES OF VISUAL ORGANIZATION
• Figure-ground - Organization depends on what we see as figure
(object) and what we perceive a ground (context).
• Similarity - Objects that have similar characteristics are perceived as
unit.
• Proximity - Objects close together in space or time perceived as
belonging together.
• Continuity - We tend to perceive figures or objects as belonging
together if they appear to form a continuous pattern.
• Closure - We perceive figures with gaps in them to be complete.
• Simplicity - We tend to impose the simplest, best fitting, interpretation
to any stimulus.
• Common Fate - Visually perceived images that move toward
each other are seen as forming a common object.

27. GESTALT PRECEPTS
 The whole is greater than the sum of its parts.
 Reality is different than perception
 Experience changes perception

28. Figure vs. Ground
One of the fundamental issues in
visual 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 usually
critical in this respect and will
often provide good information

29. Figure vs. Ground

30. Figure vs. Ground

31. Figure vs. Ground

32. Figure vs. Ground

33. Figure vs. Ground

34. Figure vs. Ground
An issue related to figure/ground is the following.
As we have observed visual scenes can be
somewhat ambiguous, and can be seen in
different ways. What are the
cues that allow us to see one
perspective over another?
Is the picture on the left a picture
of a young stylish woman, or of
an old woman?

35. Similarity
Items that look similar will be seen as
parts of the same form.
Do you see
columns or
rows?

36. Similarity
Similar objects are seen as independent
entities.

37. Proximity
Things that are relatively close to one
another tend to be grouped together

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

39. Proximity
The cluster has a separate identity outside
the organized group.

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

41. Continuity
Continuity of shape
Continuity of line

42. Continuity
An assumption is made that a certain
continuity exists due to generalization.

43. Continuity

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

45. Closure
The mind has an uncanny ability to
imagine shapes where there are none

46. Closure
The mind has an uncanny ability to
distinguish form from inadequate cues.

47. Closure

48. Closure
In the 1950’s this photograph of a shadow
formed by a tree caused quite a stir in
Argentina.

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

50. Continuity and Closure
What does the sign say?

51. Common Fate
Visually perceived images that move toward
each 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 they
appear visible.

52. Common Fate

53. Common Fate

54. Common Fate

55. Common Fate

56. Simplicity
We tend to impose the simplest, best fitting,
interpretation to any stimulus.
In the image
on the left, we
tend to reduce
the figures to
the simplest
shapes.