Perception is how the brain interprets and makes sense of sensations. There are several principles that govern perception, including constancies that allow us to perceive objects as having consistent size, shape, and brightness regardless of distance or lighting. Gestalt principles describe how we group objects visually based on proximity, similarity, closure, and other factors. Depth perception uses monocular cues like linear perspective and binocular cues like convergence and disparity to see in 3D. Perception is influenced by both internal factors like personality and motivation, and external factors like size, intensity, contrast, and motion of stimuli. Different cultures and religions may perceive visual patterns differently.

1. PERCEPTION
Dr. Sushma Rathee
Assistant Clinical Psychologist , PGIMER,
Chandigarh
Email: sushmaratheecp@gmail.com
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2. What is Perception
• Perception is the method by which the brain takes all the
sensations people experience at any given moment and allows
them to be interpreted in some meaningful fashion. Perception
has some individuality to it.

3. The Constancies:
1. Size constancy: the tendency to interpret an object as always
being the same actual size, regardless of its distance.
2. Shape constancy: the tendency to interpret the shape of an
object as being constant, even when its shape changes on the
retina.
3. Brightness constancy: the tendency to perceive the apparent
brightness of an object as the same even when the light
conditions change.

4. THE GESTALT PRINCIPLES:
1. Figure–ground: the tendency to perceive objects, or figures,
as existing on a background. Reversible figures visual
illusions in which the figure and ground can be reversed.
• Reversible figures, in which the figure and the ground
seem to switch back and forth.

5. • 2. Proximity: the tendency to perceive objects that are close to
each other as part of the same grouping.

6. 3. Similarity: the tendency to perceive things that look similar to
each other as being part of the same group.

7. 4. Closure: the tendency to complete figures that are
incomplete.

8. 5. Continuity: the tendency to perceive things as simply as
possible with a continuous pattern rather than with a complex,
broken-up pattern.

9. • 6. Contiguity: the tendency to perceive two things that happen
close together in time as being related.

10. 7. Common region: the tendency is to perceive objects that are in
a common area or region as being in a group.

11. DEPTH PERCEPTION:
• The ability to perceive the world in three dimensions.
• Various cues exist for perceiving depth in the world. Some
require the use of only one eye (monocular cues) and some are
a result of the slightly different visual patterns that exist when
the visual fields of both eyes are used (binocular cues).
• Monocular cues are often referred to as pictorial depth
cues because artists can use these cues to give the
illusion of depth to paintings and drawings.

12. Monocular cues:
1. Linear perspective: the tendency for parallel lines to appear to
converge on each other.

13. 2. Relative size: perception that occurs when objects that a person
expects to be of a certain size appear to be small and are,
therefore, assumed to be much farther away.

14. 3. Overlap (interposition): the assumption that an object that
appears to be blocking part of another object is in front of the
second object and closer to the viewer.
4. Aerial (atmospheric): perspective the
haziness/cloudiness that surrounds objects
that are farther away from the viewer,
causing the distance to be perceived as
greater.

15. 5. Texture gradient: the tendency for textured surfaces to appear
to become smaller and finer as distance from the viewer
increases.
6. Motion parallax: the perception of motion of objects in which
close objects appear to move more quickly than objects that are
farther away.

16. 7. Accommodation: as a monocular cue, the brain’s use of
information about the changing thickness of the lens of the eye in
response to looking at objects that are close or far away.

17. BINOCULAR CUES:
1. Convergence: the rotation of the two eyes in their sockets to
focus on a single object, resulting in greater convergence for
closer objects and lesser convergence if objects are distant.

18. 2. Binocular disparity: the difference in images between the two
eyes, which is greater for objects that are close and smaller for
distant objects.

19. Perceptual Selection:
Internal factors include:
1. Personality – Personality traits influence how a person selects
perceptions. For instance, conscientious people tend to select
details and external stimuli to a greater degree.
2. Motivation – People will select perceptions according to what they
need in the moment. They will favor selections that they think will
help them with their current needs, and be more likely to ignore
what is irrelevant to their needs.
3. Experience – The patterns of occurrences or associations one has
learned in the past affect current perceptions. The person will select
perceptions in a way that fits with what they found in the past.

20. External factors include:
1. Size – A larger size makes it more likely an object will be selected.
2. Intensity – Greater intensity, in brightness, for example, also
increases perceptual selection.
3. Contrast – When a perception stands clearly out against a
background, there is a greater likelihood of selection.
4. Motion – A moving perception is more likely to be selected.
5. Repetition – Repetition increases perceptual selection.
6. Novelty and familiarity – Both of these increase selection. When a
perception is new, it stands out in a person’s experience. When it is
familiar, it is likely to be selected because of this familiarity.

21. Religion and perception:
• People of different religions have different perspectives on life,
but do they also have different visual perceptions? It might be
clichéd to say that religious people see the world differently, but
new research finds that Dutch Calvinists notice embedded
visual patterns quicker than their atheist compatriots.
• Culture has long been known to distort visual perception,
says Bernhard Hommel, a psychologist at Leiden University in
the Netherlands who led the new study.
• For example, one previous experiment found that Asians tend to
dart their eyes around a photograph, while North Americans fix
on specific people.

22. Age and Perception: