Perception: definition, nature, importance, gestalt laws of grouping, bottoms up top down processing, perceptual process and perceptual constancy. #psychology #perception #perceptualgrouping #perceptualconstancy

1. Perception
Prof. Jigyasa Thakur,
Renaissance University,
Indore, M.P.

3. Experimental Psychology
Concept
Perception: Stimulus/ Stimuli response, under influence of various
factors (need, motive, goal, environment, internal function, experience),
resulting in certain behavioral output.

4. Key Words:
• Sensation:
• Attention: Focused, Goal oriented, Selective
Types: Selective, Divided, (Study: overt, covert in visual field)
• Core Beliefs (Schemas), Need and Motives:
• Perception: ? (Subliminal)?

5. Sensation
Physical process of receiving information from environment via senses.

6. Attention
: Process which compels an individual to select a particular stimulus based on his
interest to focus upon

7. Constancy
the quality of being enduring and unchanging
(Meaning? State of being constant)*

8. Proximity
Spatial closeness, nearness
(things that are close to one another tend to be grouped together)

9. illusions
an instance of a wrong or misinterpreted perception of a sensory experience.
(Stimulus is present*, representation may or may not be wrong, perception is
falsely constructed) (perceptual disturbance)

10. Subliminal Perception
Sub = below (like submarine) & Limen = threshold
Evoked by stimulus which is un-noticed i.e. below the absolute threshold
Extra Read: Iconic and Echoic Memory

11. Define Perception: “Perception is the process through which the information from outside
environment is selected, received, organized and interpreted to make it meaningful to you. This input
of meaningful information results in decisions and actions.”
“Perception may be defined as a process by which individuals organize and interpret their sensory
impressions in order to give meaning to their environment.”
Its subjective, mental process, a result of perceiving, mental representation of sensory information,
influenced by various factors.
People’s behavior is based on their perceptions of what reality is, not the reality itself.

12. Nature of Perception?
• It is a process (which is psychological, cognitive and intellectual.
• It is a mental representation as well, hence it is subjective.
• It is a response to environment stimuli.
• It is an interpretation.
• It can be changed or altered.
• It uses stored memories and past experiences.

13. Extra Read: Bruner’s Model of perceptual process

14. Types of Perception:
• Form
• Space (distance, depth: Monocular (haze, texture, relative size, linear
perspective, interposition/occlusion, accommodation), Binocular
(retinal disparity, convergence)
• Size (size, distance hypothesis,
• Time (sequence of events, separated by durations, fly & drag effect)
• Movement (retinal motion, induced motion, motion aftereffect,
apparent motion) (Phi phenomenon, stroboscopic effect, autokinetic
effect, induced motion)

15. Perception of Form:
• Form: Organization of visual fields in to objects (figures that stand
out)
• Gestaltists have proposed laws of organization under perception of
form which emphasize on grouping of objects in visual field, known as
Gestalt laws of perceptual grouping.
• Study: *Gestalt philosophy? Experiments by Gestaltists about Form.

18. Law of Figure Ground: The human eye can differentiate an object from the
surrounding. We perceive certain objects as being in the foreground and other
objects as being in the background. Let’s check the examples of this principle.

19. Law of Proximity: Tendency to group elements those are in close spatial proximity. describes
how the human eye perceives connections between visual elements. Elements that are
close to each other are perceived to be related when compared with elements that are
separate from each other.

20. Law of Continuity: Tendency to perceive object as in continuous form in simplest way
possible rather than complex form.

21. Law of Pragnanz: Pragnanz or Good Figure, tendency to perceive objects grouped
together in balanced form which makes sense. Reality is reduced to its simplest
form. (Symmetrical, Simple, Regular figure)

22. Law of Closure: Tendency to fill gaps in an object to make it whole and perceive as
whole. The edges are considered closed.

23. Law of Similarity: Tendency to group physically similar objects.

24. Law of Common fate: Tendency to perceive objects which move together and
change together.

25. : Tendency to perceive objects which move together and change together.
• Perceptual grouping is influenced by our broader assumptions and
beliefs known as Mental Models.
• Mental models: Theories in use that people rely to guide their
perceptions and behaviors.
• It helps to make sense of our environment, but may blind us from
seeing world different ways.

26. Perception of Size: Sensory information of dimensions of objects.

27. Perception of Size: Sensory information of
dimensions of objects.
Depends upon: 1. Angle of vision, 2. Distance
from the object, 3.
Perception effects: as weight of object vs size?

28. Depth perception: Visual ability to process world’s sensory information in 3D and
thus enabling us to judge the distance of the objects in surrounding.
• 1st experiment was done by Gibson and Walk in 1960, with an infant, via visual effects of a cliff.
• Monocular Cues: 2D from one eye, creates confusion in distance of object.
• Binocular Cues: builds 3D image by triangulation, to give best possible cue about the distance of
the object.
• Motion Parallax: When we are moving in a straight line, nearer objects seems to move faster as
compared to father objects. Example: Train.
• Linear Perspective: Brain deduces the depth or distance of the object depending upon the
vanishing point. Example Train Tracks – they meet and vanish. Tricks used in Paintings.

29. Movement perception: It is our ability to judge the direction and speed
of a moving object. Four factors involved are retinal motion, motion after-effect
(MAE), induced movement, stroboscopic motion.
Space perception: The visual field or surface in which things exist, move or can be
placed is called space. Space perception, process through which humans and other
organisms become aware of the relative positions of their own bodies and objects
around them.
Time perception: the subjective experience, or sense, of time, which is measured by
someone's own perception of the duration of the indefinite and unfolding of events.
*Dopamine neurons in a brain region known as the substantia nigra pars compacta
can alter the perception of time, according to new research published.

30. Illusion: a false sensory percept. Illusions of the senses, such as visual
illusions, result from the misinterpretation of sensory stimuli.
• Occurs on sensory level
• Wrong interpretation occurs on perception level
• Response is often confusing
• Stimulus is present, Response is present, Confusion occurs due to
misleading information, and hence misinterpretation.

31. Subliminal Perception: Stimulus is below the absolute threshold l

33. If you noticed the cues like Man’s shoulder insignia,
white shirt and tons of buttons with wind shield,
probably you have used your experience of seeing a
pilot. Isnt it? Or you started to see all tiny clues and
trying to understand who is he and what is he doing?

34. Above 3 letter word makes sense to
you?
Mostly not much, youre trying
bottoms up approach.

35. Now does this 3 letter word makes
to you? If yes.
You have used Bottoms up , and
probably top down hit you all of
sudden.

36. Perceptual Constancy: It remains constant,
unchanged, doesn’t matter how the environment
changes.
• Comes under Laws of: (Visual Perception)
• Size constancy : (Unchanged size of any object irrespective to other cues)
• Brightness constancy : (Recognize a visual stimulus, and form perception of
its/based on intensity of light)
• Shape constancy : (Human Figure or a Table)
• Color constancy : Color doesn’t change with lighting.
• Note: Perceptual constancy is nothing but state of being constant of what
you are seeing. Any object will remain same in its properties irrespective to
changes in environment and placements.

37. REVISE NOW: Absolute Threshold, Difference Threshold or Just noticeable threshold, Subliminal
threshold.
Example: A Mosquito bit you.
1: Mosquito bit you, you are aware you’re being bitten - THRESHOLD.
2: Mosquito bit you 4 times, you noticed atleast twice (50% of time) – ABSOLUTE THRESHOLD
(conscious) (weber’s law)
3: Mosquito bit you, you had no clue what happened, you didn’t move your hand, you didn’t itch, you
wonder why you have Malaria? – SUBLIMINAL THRESHOLD (not conscious)
4: Mosquito bit you, you itched little later, then again an Ant bit, you noticed and you can clearly tell
its not mosquito, rather something more painful. – DISCRIMINATION THRESHOLD
5: This time, again 3 Mosquitoes have bitten you, and you can tell each time which bite was more
painful or less painful – DIFFERENCE THRESHOLD (JND, weber’s formula, later worked upon by
Fechner)

38. Thank you!
• Gestalt’s perceptual grouping is specially for vision perception and
how we group stimuli, its important in discrimination.
• Perceptual constancies may sound tough, but conceptually they are
easiest.
• Bottoms up and Top down needs constant practice: most of real life
experiences have both ways. Human’s don’t decide to use just one.
• Psychophysics threshold topic is best understood with mathematical
expressions and graphs. Weber’s law and JND formula can help you
understand how in real life we created scales and norms. I have
different PPT uploaded for Psychophyics.