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
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
the discrimination of distance between
the discrimination of background and
the discrimination of depth of field
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
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.
From the lateral geniculate nucleus, the impulses
radiate to the primary visual cortex of the
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
The retina is not evenly represented but, instead,
more primary cortex is devoted to images at or near
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.
PERCEPTION is the process of identifying the
sensory input, and categorizing it accordingly.
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
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
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
Photo taken while hallucinating.
4. Personality characteristics of the observer.
A. Motivation - perceiving what we want to
B. Expectation - perceiving what we ought to
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
Observe the path the jet of
water takes from its origin
to the end of the arc.
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.
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
how an individual will
perceive the same
differently if scanning
for different things.
1 - looking at composition
3 - looking for age
5 - looking for dress
7 - looking for relationships
Hi Vishwall Imigmashun calss.
Aoccdrnig to rceent rscheearch at Cmabrigde Uinervtisy,
it deosn't mttaer in waht oredr the lrttees in a wrod are, the
olny iprmoetnt tihng is taht the frist and lsat ltteer be at the
rghit pclae. The rset can be a total mses and you can sitll
raed it wouthit porbelm.
Tihs is bcuseae the huamn mnid deos not raed ervey lteter
by istlef, but the wrod as a wlohe.
Eonjy, Gozvendn :)
7. Observation patterns - Gestalt
The next segment will deal with these in greater
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.
Gestalt is a German word that means: a
whole entity or entirety.
We see everything
f or the f irst time. .
We see everything for the first time.
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.
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
• Proximity - Objects close together in space or time perceived as
• 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.
The whole is greater than the sum of its parts.
Reality is different than perception
Experience changes perception
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
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?
Items that look similar will be seen as
parts of the same form.
Do you see
Similar objects are seen as independent
Things that are relatively close to one
another tend to be grouped together
When elements are arranged in groups
that define an object, we tend to see the
object and not the elements.
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 of shape
Continuity of line
An assumption is made that a certain
continuity exists due to generalization.
In the 1950’s this photograph of a shadow
formed by a tree caused quite a stir in
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 toward
each other are seen as forming a common
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