Perceptual Organization: Lecture by Imran Ahmad Sajid for BS Social Work/Sociology, ISSG, UOP-April...

Imran A. Sajid

Perceptual Organization

Imran Ahmad Sajid, T.A., ISSG, UOP

Imran A. SajidImran A. Sajid

• Perception (psychology), process by which humans interpret and organize sensation to produce a meaningful experience of the world.

• Sensation usually refers to the immediate, relatively unprocessed result of stimulation of sensory receptors in the eyes, ears, nose, tongue, or skin.

• Perception, on the other hand, is the interpretation and organization of the sensory inputs into meaning full experience of the world.

• In practice, sensation and perception are virtually impossible to separate, because they are part of one continuous process.


• Our sense organs translate physical energy from the environment into electrical impulses processed by the brain.

• For example, light, in the form of electromagnetic radiation, causes receptor cells in our eyes to activate and send signals to the brain.

• But we do not understand these signals as pure energy.

• The process of perception allows us to interpret them as objects, events, people, and situations.


• Without the ability to organize and interpret sensations, life would seem like a meaningless jumble of colors, shapes, and sounds.

• A person without any perceptual ability would not be able to recognize faces, understand language, or avoid threats.

• Such a person would not survive for long.


Perception

• Perception is the process of obtaining knowledge of external objects and events, by means of sense (Ross Stagner and T.F. Karwoski, 1952, p.207).

• The sorting out, interpretation, analysis, and integration of stimuli by the sense organs and brain (Robert Feldman, p.91).


• Suppose you had been born blind, but now were suddenly able to see. Suppose further that you now see the world as other adults do.

• What do you think, would you know what you are looking at?

• No, you would only see shapes, colours, contours, brightness before you, but what they meant would be a puzzle.


Senden, M. Von Experiment--1932

• 66 blind persons from birth underwent a cataract operation, permitting vision at a delayed age.

• Finding: The patient is aware of being visually stimulated, but he does not identify objects


He could distinguish visually between a ball and a block, but he did not know which was which until allowed to handle them.


The girl could see only a patch of colours coming towards her, but only when she touches it does she exclaims, Wah, that’s Kitty!


Were not able to tell which card was shorter until touched them.


How We Organize Our Perception?

Can you read this sentence when it is upside down?

Probably yes.

Can you read this sentence when it is upside down?


Reason???

• Knowledge and experience allowed you to understand the text.– Knowledge of letters shape, – Experience in reading text upside down (may be),

• Without knowledge of the letters shape, you would perceive them as meaningless.


Can you perceive the meaning of the following?

• 你能读这句话时，它是在中国吗？(Chinese)

• それが日本語であるときにこの文章を読むことができますか？ (Japanese)Most probably, NOT… Because you do not have the knowledge of Chinese or Japanese letters and their shapes.


• Note that in the example above, you did not stop to read every single letter carefully.

• Instead, you probably perceived whole words and phrases.

• You may have also used context to help you figure out what some of the words must be

uu

down


How people perceive a well-organized pattern or whole, instead of many

separate parts???

• This is a topic of interest in Gestalt psychology. • According to Gestalt psychologists, the whole is

different than the sum of its parts. • Gestalt is a German word meaning configuration or

pattern• a set of things considered as a whole and regarded

as amounting to more than the sum of its parts.


A. Figure-Ground Approach

• Not only does perception involve organization and grouping, it also involves distinguishing an object from its surroundings.

• Notice that once you perceive an object, the area around that object becomes the background.

• For example, when you look at these slides, the wall and everything else behind it becomes the background.

• The object, or figure, is closer to you, and the background, or ground, is farther away.


• Consider the accompanying illustration 1.

• You may see a white vase as the figure, in which case you will see it displayed on a dark ground.

• However, you may also see two dark faces that point toward one another.

• Notice that when you do so, the white area of the figure becomes the ground.

Point: We do not just passively respond to visual stimuli that happen to fall on our retina. Instead, actively try to organize and make sense of what we see

1


• It is likely that you will perceive the form of a dog in this picture.

• The dog represents a gestalt, or perceptual whole.

• Although you can see the individual parts that make up the figure, putting them together forms something greater than the individual parts.

• The whole is different from the sum of its parts.

Point: We do not just passively respond to visual stimuli that happen to fall on our retina. Instead, actively try to organize and make sense of what we see.


Factors Affecting Perception

• External Factors1. Change2. Repetition 3. Size4. Intensity

• Internal Factors1. Motives2. Set or Expectancy 3. Needs and Values


B. Principles of Perception

1. Closure2. Proximity3. Similarity4. Simplicity


1. Closure

• Groupings are usually made in terms of enclosed or complete figures rather than open ones.

• We tend to ignore the breaks in the given figure and concentrate on the overall form

Closure: something that closes opening


• In other words, • we prefer complete forms to incomplete

forms. • Thus, in the drawing above, we mentally close

the gaps and perceive a picture of a duck. • This tendency allows us to perceive whole

objects from incomplete and imperfect forms.


2. Proximity

• Elements that are closer together are grouped together. As a result, we tend to see the given circles on the left as in vertical columns, and the circles on the right as grouped into horizontal rows.

• Pair of dots rather than a row of single dots

.. .. .. .. .. .. ..


3. Similarity

• Elements that are similar in appearance are grouped together.

• We see, then, vertical columns of circles and squires instead of horizontal mixed rows in the given picture.


4. Simplicity• In a general sense, the overriding

gestalt principle is simplicity: • When we observe a pattern, we

perceive it in the most basic, straightforward manner that we can.

• Most of us see the given figure on the right as a square with lines on two sides, rather than as the block letter “W” on top of the letter “M”.

• If we have a choice of interpretations, we generally opt for the simple one.


U U


R


C. Feature Analysis

• We perceive a shape, pattern, object, or scene by reacting first to the individual elements that make it up.

• These individual components are then used to understand the overall nature of what we are perceiving.


• E.g. the letter “R” is a combination of a vertical line, a diagonal line, and a half circle.

• According to feature analysis, when we encounter a stimulus—such as a letter—our brain’s perceptual processing system initially responds to its component parts.

• Each of these parts is compared with information about components that is stored in memory.

• When the specific components we perceive match up with a particular set of components that we have encountered previously, we are able to identify the stimulus.


Perception as a Two-Stage Process

1. Pre-attentive stage– In this stage we focus on the physical features of a

stimulus, such as its size, shape, colour, orientation, or direction of movement.

– This initial stage takes little or no conscious effort.

2. Focused attention stage– We pay attention to particular features of an

object, choosing and emphasizing features that were initially considered separately.


Is perception based mainly on consideration of the component

parts of a stimulus, or

is it grounded primarily in perception of the stimulus as a

whole?


C. Top-Down and Bottom-Up Processing

• Ca- yo- re-d t-is -en-en-e, w-ic- ha- ev-ry -hi-d l-tt-r m-ss-ng? • “Can you read this sentence, which has every third letter

missing?”• If perception were based primarily on breaking down a

stimulus into its most basic elements, understanding the sentence, as well as other ambiguous stimuli, would not be possible.

• The fact that you were probably able to recognize such an imprecise stimulus illustrates that perception proceeds along two different avenues, called top-down processing and bottom-up processing.


Top-down processing

• We process a stimulus according to our prior – knowledge, – experience, – expectations, and – motivations.

• You were able to figure out the meaning of the sentence with the missing letters because of your prior reading experience.

• your expectations played a role in your being able to read the sentence.

• You were probably expecting a statement that had something to do with psychology.


Importance of Context

• Most of us perceive that the first row consists of the letters A through F, while the second contains the numbers 10 through 14.

• But take a more careful look and you’ll see that the “B” and the “13” are identical.

• Clearly, our perception is affected by our expectations about the two sequences—even though the two stimuli are exactly the same.

Point: Perception is affected by prior knowledge, experience, expectations, and motivations.


Bottom-up Processing

• consists of the progression of recognizing and processing information from individual components of a stimuli and moving to the perception of the whole.

• Some perception, then, occurs at the level of the patterns and features of each of the separate letters.

Ca- yo- re-d t-is -en-en-e, w-ic- ha- ev-ry -hi-d l-tt-r m-ss-ng?


Bottom-Up Processing

Prior Knowledge, Experience, etc.

Prior Knowledge, Experience, etc.

Stimuli ProcessingStimuli Processing

PerceptionPerception

Stimuli InputCreated by Dr. Gordon Vessels 2005

Imran A. SajidImran A. SajidTop-Down Processing

Stimuli ProcessingStimuli Processing

PerceptionPerception

Stimuli Input

Prior Knowledge, Experience, etc. Prior Knowledge, Experience, etc.

Personality Temperament

Culture Social Class

Values Beliefs

Prejudices Attitudes

Immediate Mental Set

Presence of Authority

Present Fatigue Energy Level

Prior Stimuli Perceived

Occupation Education

Needs, Moods Mental Health

Knowledge Vocabulary

Specific Life Experiences

Long-term Memory Schemas

Created by Dr. Gordon Vessels 2005

Imran A. Sajid

What do you see? A face looking

down? The word Liar in script or cursive? Those who first read stories about deception were more inclined than others to see

the word Liar.

What do you see? The word liar in script or cursive? A face looking down? Those shown artwork with faces were more inclined than others to see the word liar.

Arranged by Dr. Gordon Vessels 2004


• Top-down and bottom-up processing occur simultaneously, and interact with each other, in our perception of the world around us.

• Bottom-up processing permits us to process the fundamental characteristics of stimuli, whereas top-down processing allows us to bring our experience to bear on perception.


D. Perceptual Constancy

• Perceptual constancy is a phenomenon in which physical objects are perceived as unvarying and consistent despite changes in their appearance or in the physical environment.

we see objects as the same size at different distances because they stay the same size relative to surrounding objects.


E. Depth Perception• Our eyes are spaced about 7 cm (about 3 in)

apart, the left and right retinas receive slightly different images.

• This difference in the left and right images is called binocular disparity.

Hold a pencil/pen at arm’s length and look at it, first with one eye and than with the other.

Bring it about 6 inches from your eyes and look at it again.


Monocular Cues• In some instances, certain cues permit us to obtain

sense of depth and distance with just one eye. These cues are know as monocular cues.

• One monocular cue—motion parallax– is the change in position of an object on the retina as the head moves from side to side.

• The brain is able to calculate the distance of the object by the amount of change in the retinal image.

If two objects are the same size, the one that makes a smaller image on the retina is farther away than the one that provides a larger image—an example of the monocular cue of relative size.


Recap

• Among the Gestalt Laws of organization are closure, proximity, similarity, and simplicity.

• People do not respond passively to visual stimuli; rather they try to separate a given figure from the background.

• Feature analysis considers how people perceive a stimulus, break it down into the individual elements that make it up, and then use those elements to understand what they are seeing.

• Perception occurs through top-down and bottom-p processing. • Depth perception occurs because of binocular disparity,

monocular cues, and relative size.


Review Questions

• Match each of the following organizational laws with its meaning. a) Closureb) Proximityc) Similarityd) Simplicity1. Elements close together are grouped together. 2. Patterns are perceived in the most basic, direct manner

possible. 3. Groupings are made in terms of complete figures. 4. Elements similar in appearance are grouped together.

a-3; b-1; c-4; d-2


1. ____ analysis deals with the way in which we break an object down into its component pieces in order to understand it???

• Feature analysis1. When a car passes you on the road and

appears to shrink as it gets fartehr away, which perceptual phenomenon permits you to realize that the car is not in fact getting smaller???

• Perceptual constancy


THANKS Courtesy: Imran Ahmad Sajid, T.A., ISSG, University of Peshawar. [email protected]

mailto:[email protected]


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Perceptual Organization: Lecture by Imran Ahmad Sajid for BS Social Work/Sociology, ISSG, UOP-April...

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