09 sensation -perception

Sensation and Sensation and PerceptionPerception

DR Mohamed Youssef DR Mohamed Youssef AbuziedAbuzied

Sensation & Sensation & PerceptionPerception

“ The study of perception is concerned with identifying the process through which we interpret and organize sensory information to produce our conscious experience of objects and object relationship.”

We are now turning our attention to the topic of “Sensation & Perception,” a specialty area within Psychology that works at understanding how our senses work & how we perceive stimuli in the environment. So, with no further delay….

Let’s begin with some Let’s begin with some basic definitions…basic definitions… SSense ense – Physical system that receives physical – Physical system that receives physical

stimulation from surrounding environment and stimulation from surrounding environment and translates that stimulation into an electrochemical translates that stimulation into an electrochemical messagemessage

SSensaensationtion – The electrochemical message in neurons – The electrochemical message in neurons transmitting information from the sense organ to the transmitting information from the sense organ to the brain.brain.

PPerceptionerception – Processing of information done by the – Processing of information done by the brain – mental processes that organize and interpret brain – mental processes that organize and interpret sensory information that has been transmitted to the sensory information that has been transmitted to the brain.brain.

TransductionTransduction So the brain’s “language” is So the brain’s “language” is

electrochemical! electrochemical!

All senses involve something called All senses involve something called receptor cellsreceptor cells. Their job is to transduce . Their job is to transduce (transform or even “translate”) physical (transform or even “translate”) physical stimulation/physical energy from the stimulation/physical energy from the environment into electrochemical environment into electrochemical messages that can be understood by the messages that can be understood by the brain. brain.

The mystery of feature The mystery of feature detectors…detectors… Feature detectors Feature detectors are cortical neurons are cortical neurons

that respond to specific features of a that respond to specific features of a scene (e.g., particular edges, lines, scene (e.g., particular edges, lines, angles and movements)angles and movements)

The brain then needs to assemble the The brain then needs to assemble the whole image from these specific features.whole image from these specific features.

“…“…perceptions arise from the interaction perceptions arise from the interaction of many neuron systems, each of many neuron systems, each performing a simple task.” performing a simple task.”

66 Organizational Behavior / Organizational Behavior / PerceptionPerception

PerceptionPerception

“ “ Perception is the process of receiving information about and Perception is the process of receiving information about and making sense of the world around us. It involves deciding making sense of the world around us. It involves deciding which information to notice, how to categorize this which information to notice, how to categorize this information and how to interpret it within the framework of information and how to interpret it within the framework of existing knowledge.existing knowledge.

“ “ A process by which individuals organize and interpret their A process by which individuals organize and interpret their sensory impressions in order to give meaning to their sensory impressions in order to give meaning to their environment.environment.

Perception DefinedPerception Defined The process by which we become aware of objects The process by which we become aware of objects

and events in the external world.and events in the external world.

The process of The process of making sense making sense of the world around of the world around us.us.

Many people ignore the fact that all of us are Many people ignore the fact that all of us are different and that these differences equip us to different and that these differences equip us to view the world from our very own vantage points. view the world from our very own vantage points. Usually we spend more energy defending our own Usually we spend more energy defending our own position than understanding others.position than understanding others.

Where does the triangle begin?


The Perceptual ProcessThe Perceptual Process

1.1. SensationSensation– An individual’s ability An individual’s ability

to detect stimuli in the to detect stimuli in the immediate immediate environment.environment.

2.2. SelectionSelection– The process a person The process a person

uses to eliminate some uses to eliminate some of the stimuli that have of the stimuli that have been sensed and to been sensed and to retain others for retain others for further processing.further processing.

3.3. OrganizationOrganization– The process of The process of

placing selected placing selected perceptual stimuli perceptual stimuli into a framework for into a framework for “storage.”“storage.”

4.4. TranslationTranslation– The stage of the The stage of the

perceptual process perceptual process at which stimuli are at which stimuli are interpreted and interpreted and given meaning.given meaning.


Factors influencing Factors influencing perceptionperception

A number of factors operate to shape and A number of factors operate to shape and

sometimes distort perception. These factors can sometimes distort perception. These factors can

reside in the reside in the perceiverperceiver, in the object or , in the object or targettarget

being perceived or in the context of thebeing perceived or in the context of the situation situation

in which the perception is made.in which the perception is made.


Factors influencing PerceptionFactors influencing PerceptionFactors in the perceiver• Attitudes• Motives• Interests• Experience• Expectations

Perception

Factors in the Target• Motion• Sounds• Size• Background• Proximity• Similarity

Factors in the situation• Time• Work Setting• Social Setting


Perceptual organizationPerceptual organization

It is the process by which we group outside stimuli It is the process by which we group outside stimuli into recognizable and identifiable patterns and whole into recognizable and identifiable patterns and whole objects.objects.

Certain factors are considered to be important Certain factors are considered to be important contributors on assembling, organizing and contributors on assembling, organizing and categorizing information in the human brain. These categorizing information in the human brain. These areare

- Figure groundFigure ground- Perceptual groupingPerceptual grouping

Perceptual Perceptual organizationorganization Three Principles of Organization:Three Principles of Organization:

– A) Binary Opposition A) Binary Opposition (all things in pairs)(all things in pairs) male/female, short/tall, white/black, good/badmale/female, short/tall, white/black, good/bad

– B) Already formed social categoriesB) Already formed social categories 101 students, sorority sisters, UK basketball 101 students, sorority sisters, UK basketball

players, Italiansplayers, Italians– C) We also organize by similaritiesC) We also organize by similarities

sizesize ( (big buildingsbig buildings), ), colorcolor ( (things that are things that are purplepurple), ), spacespace ( (things from Hawaiithings from Hawaii), ), smellsmell ((things that make us hungrythings that make us hungry), ), functionfunction ((computer, phone, TV, DVD, VCR, CD player, computer, phone, TV, DVD, VCR, CD player, pager, palm)pager, palm)

The Cognitive Approach emphasizes The Cognitive Approach emphasizes that people are shaped (& differ. that people are shaped (& differ. from each other) because their from each other) because their perceptions & their thought perceptions & their thought processes differ. So understanding processes differ. So understanding some background information on some background information on how we perceive things in our how we perceive things in our environment may help assist us in environment may help assist us in our understanding of the Cognitive our understanding of the Cognitive approach. approach.

Schemas and Schemas and Perceptual SetPerceptual Set

A A perceptual set perceptual set is…is… A mental predisposition to perceive A mental predisposition to perceive

one thing and not another”one thing and not another”

This is based on experiences, This is based on experiences, assumptions and expectations. assumptions and expectations.

What shapes our What shapes our perceptual sets?perceptual sets? What things do you think might affect What things do you think might affect

our perceptual sets (i.e., our tendency our perceptual sets (i.e., our tendency to perceive things in certain ways)?to perceive things in certain ways)?

Context effectsContext effects Past experiencesPast experiences Effects of our cultureEffects of our culture

Schematas or Schematas or Cognitive FrameworksCognitive Frameworks

To eliminate the To eliminate the chaos of life (entropy) chaos of life (entropy) and and help make sense of the world, we help make sense of the world, we simplifysimplify and and reduce reduce our worldour world

We put our “selected” data in cognitive We put our “selected” data in cognitive “folders”“folders”– Also called: Also called: SchemataSchemata or or Cognitive FrameworksCognitive Frameworks

Schemas Schemas

Another word used to describe perceptual set Another word used to describe perceptual set is is schemasschemas..

Schemas Schemas can influence our perception can influence our perception because we tend to see things that we because we tend to see things that we expect to see or wish to. expect to see or wish to.

We interpret things based on similar things We interpret things based on similar things we have experienced in the past –this is we have experienced in the past –this is called called assimilation.assimilation.

Schemas…..Schemas….. Now what do you think Now what do you think would happen if we would happen if we receive new receive new information that information that doesn’t not fit our doesn’t not fit our schemasschemas??

When we receive new When we receive new information we can information we can ignore it (!) ignore it (!)

or we can change our or we can change our schemasschemas to fit the new to fit the new information. This is information. This is called called accommodation.accommodation.

Schemas are almost like a box that we put information into. The way we organize compartments in the box is based on things like our past experiences, contexts, etc. and this influences our perceptions!

Gestalt laws of Gestalt laws of groupinggrouping

A major aspect of Gestalt psychology is that A major aspect of Gestalt psychology is that it implies that the mind understands external it implies that the mind understands external stimuli as whole rather than the sum of their stimuli as whole rather than the sum of their parts. The wholes are structured and parts. The wholes are structured and organized using grouping laws. These laws organized using grouping laws. These laws deal with the sensory modality vision deal with the sensory modality vision however there are analogous laws for other however there are analogous laws for other sensory modalities . Through the 1930s and sensory modalities . Through the 1930s and '40s Wertheimer, Kohler and Koffka '40s Wertheimer, Kohler and Koffka formulated many of the laws of grouping formulated many of the laws of grouping through the study of visual perception.through the study of visual perception.

Law of ProximityLaw of Proximity

– – The law of proximity states that The law of proximity states that when an individual perceives an when an individual perceives an assortment of objects they perceive assortment of objects they perceive objects that are close to each other as objects that are close to each other as forming a group. For example, in the forming a group. For example, in the figure illustrating , we perceive the figure illustrating , we perceive the collection of circles to be in groups. collection of circles to be in groups.

Law of SimilarityLaw of Similarity

– – The law of similarity states that The law of similarity states that elements within an assortment of elements within an assortment of objects will be perceptually grouped objects will be perceptually grouped together if they are similar to each together if they are similar to each other. This similarity can occur in the other. This similarity can occur in the form of shape, colour, shading or other form of shape, colour, shading or other qualities .qualities .

Law of ClosureLaw of Closure

– – The law of closure states that The law of closure states that individuals perceive objects , as being individuals perceive objects , as being whole when they are not complete. We whole when they are not complete. We tend to complete the incomplete tend to complete the incomplete Specifically, when parts of a whole Specifically, when parts of a whole picture are missing, our perception fills picture are missing, our perception fills in the visual gap. in the visual gap. The purpose of The purpose of completing a regular figure is in order to completing a regular figure is in order to increase the regularity of surrounding increase the regularity of surrounding stimuli.stimuli.

Law of SymmetryLaw of Symmetry

– – The law of symmetry states that the The law of symmetry states that the mind perceives objects as being mind perceives objects as being symmetrical and forming around a symmetrical and forming around a center point. It is perceptually pleasing center point. It is perceptually pleasing to be able to divide objects into an even to be able to divide objects into an even number of symmetrical parts. number of symmetrical parts. Therefore, Therefore, when two symmetrical elements are when two symmetrical elements are unconnected the mind perceptually unconnected the mind perceptually connects them to form a coherent connects them to form a coherent shape. shape.

– – Objects are perceived as lines that Objects are perceived as lines that move along the smoothest path. We move along the smoothest path. We perceive elements of objects to have perceive elements of objects to have trends of motion, which indicate the trends of motion, which indicate the path that the object is on. path that the object is on. The law of The law of continuity implies the grouping continuity implies the grouping together of objects that have the same together of objects that have the same trend of motion and are therefore on trend of motion and are therefore on the same path. the same path.

Law of Common Law of Common Fate Fate

Law of ContinuityLaw of Continuity

– – The law of continuity The law of continuity states that elements of states that elements of objects tend to be groupedobjects tend to be grouped together, and therefore together, and therefore integrated into perceptual wholes if they are integrated into perceptual wholes if they are

aligned within an object . We are less likely to aligned within an object . We are less likely to group elements with sharp abrupt directional group elements with sharp abrupt directional changes as being one object.changes as being one object.

The sense-datum theory can say, The sense-datum theory can say, however, that we arehowever, that we areindirectlyindirectly aware of ordinary objects: that is, aware of ordinary objects: that is, aware of them by being aware of aware of them by being aware of sense-data.sense-data.

The Naive Theory of The Naive Theory of PerceptionPerception (A.K.A: Direct (A.K.A: Direct Realism)Realism)

The Not-so-Naive Theory The Not-so-Naive Theory of Perceptionof Perception (AKA: (AKA: Indirect Realism)Indirect Realism)

The Not-so-Naive but The Not-so-Naive but Totally Crazy Theory of Totally Crazy Theory of Perception Perception (AKA: (AKA: Idealism)Idealism)

What is Attention?What is Attention?

ability to focus on a taskability to focus on a task ability to concentrateability to concentrate refers to the allocation of refers to the allocation of

processing resources processing resources

Attention Attention

In daily language it refers to In daily language it refers to concentration concentration

Attention has two broad Attention has two broad dimensions :dimensions :

a-a- selectivity b- intensityselectivity b- intensity

Attention Attention

Quality of information processing :Quality of information processing : Perception ,processing and storing Perception ,processing and storing

of information wit a good intensityof information wit a good intensity So Attention can be defined as the So Attention can be defined as the

state of the processing system that state of the processing system that is optimally tuned in terms of is optimally tuned in terms of selectivity and intensityselectivity and intensity

Attentional BehaviorAttentional Behavior

Now more dimensions will appear Now more dimensions will appear

E.g. Divided Vs Sustained E.g. Divided Vs Sustained attentionattention

Different Aspects of Different Aspects of AttentionAttention

selective attentionselective attention divided attentiondivided attention automaticityautomaticity

Selective AttentionSelective Attention

Difficult to attend to more than one Difficult to attend to more than one thing at the same timething at the same time

Trying to attend to one task over Trying to attend to one task over another requires another requires selective attentionselective attention

Selective Attention (Visual)Selective Attention (Visual) slower to name color when word slower to name color when word

says a different color than to name says a different color than to name the color of an colored squarethe color of an colored square

why does this happen?why does this happen?

– reading is an automatic processreading is an automatic process– color naming is a controlled processcolor naming is a controlled process– automatic process of reading automatic process of reading

interferes with our ability to interferes with our ability to selectively attendselectively attend to ink color to ink color

Selective Attention Selective Attention (Auditory)(Auditory)

Dichotic listeningDichotic listening In a typical dichotic listening task, Ss In a typical dichotic listening task, Ss

hear two messages hear two messages simultaneously...one message in one simultaneously...one message in one ear and one message in the other;ear and one message in the other;

As they are listening, they are asked As they are listening, they are asked to 'shadow' one of the messages (i.e. to 'shadow' one of the messages (i.e. repeat back the words from one repeat back the words from one message only message only

Theoretical Theoretical Interpretations of Interpretations of Selective AttentionSelective Attention

Bottleneck theories or Bottleneck theories or filter filter theories theories

bottleneck is a mechanism that bottleneck is a mechanism that limits the amount of information limits the amount of information to be attended toto be attended to

what gets through? what is what gets through? what is selectedselected and when? and when?

Early selectionEarly selection

Broadbent (1958) proposed that Broadbent (1958) proposed that physical characteristics of messages physical characteristics of messages are used to select one message for are used to select one message for further processing and all others are further processing and all others are lost .lost .He postulated that the many He postulated that the many signals entering the central nervous signals entering the central nervous system in parallel are held for a system in parallel are held for a very short time in a temporary very short time in a temporary “buffer.” “buffer.”

AttenuationAttenuation

Treisman (1964) proposed that Treisman (1964) proposed that physical characteristics are used physical characteristics are used to select one message for full to select one message for full processing and other messages processing and other messages are given partial processingare given partial processing

Late selectionLate selection

Deutsch & Deutsch (1963) Deutsch & Deutsch (1963) proposed that all messages get proposed that all messages get through, but that only one through, but that only one response can be made (late response can be made (late selection)selection)

Divided Attention and Divided Attention and Dual Task PerformanceDual Task Performance

trying to attend to two stimuli at trying to attend to two stimuli at once and making multiple once and making multiple responses rather than making responses rather than making one response to multiple stimuli one response to multiple stimuli (interference)(interference)

Sustained attention: Sustained attention: vigilancevigilance

Sustained attention, or vigilance, Sustained attention, or vigilance, as it is more often called, refers as it is more often called, refers to the state in which attention to the state in which attention must be maintained over time. must be maintained over time.

Two-process” theories Two-process” theories of attention. of attention. Controlled search Controlled search and and automatic automatic

detectiondetection. . Controlled search Controlled search is easily is easily

established and is largely under the established and is largely under the individual’s control in that it can be individual’s control in that it can be readily altered or even reversed. It is readily altered or even reversed. It is strongly dependent on the stimulus strongly dependent on the stimulus load. It has been suggested that it load. It has been suggested that it uses short-term memory. uses short-term memory.

Automatic DetectionAutomatic Detection..

By contrast, automatic detection, By contrast, automatic detection, or automatic processing, operates or automatic processing, operates in long-term memory and is in long-term memory and is dependent upon extensive dependent upon extensive learning. It comes into operation learning. It comes into operation without active control or attention without active control or attention by the individual, it is difficult to by the individual, it is difficult to alter or suppress.alter or suppress.

Broadly speaking, the two types Broadly speaking, the two types of attention can be characterized of attention can be characterized as as focalfocal and and automaticautomatic..

Someone who is focally attentive Someone who is focally attentive is highly aware, consciously in is highly aware, consciously in control, and selective in handling control, and selective in handling sensory phenomena. A person in sensory phenomena. A person in such a state also uses the brain such a state also uses the brain for short-term storage. Focal for short-term storage. Focal attention makes great demands attention makes great demands on brain capacityon brain capacity

Automatic attention Automatic attention makes fewer makes fewer demands but is relatively demands but is relatively inflexible, as it cannot cope with inflexible, as it cannot cope with the unexpected.the unexpected.

The focal and automatic modes The focal and automatic modes may be illustrated by a driving may be illustrated by a driving example: a new driver has to example: a new driver has to attend to gear shifting in a focal attend to gear shifting in a focal way (actively thinking about it), way (actively thinking about it), while an experienced driver while an experienced driver changes gears automatically (not changes gears automatically (not needing to think about it).needing to think about it).

09 sensation -perception

Documents