Cognition (mental activity or mental processes)

Cognition (Latin: cognoscere, "to know" or "to recognize") refers to the acquisition, storage, transformation, and use of knowledge. Cognition can be natural or artificial, conscious or unconscious.

It is a faculty of mental processes such as learning, memory, perception, thinking, problem solving, reasoning, decision making etc.

Characteristics

The cognitive processes are active, rather than passive

The cognitive processes are remarkably efficient and accurate

The cognitive processes Handle positive information better than negative information

The cognitive processes are interrelated with one another, they do not operate in isolation

many cognitive processes rely on both bottom-up and top-down processing

Sensation The processes by which our sense organs receive

information from the environment.

Transduction The process by which physical energy is

converted into sensory neural impulses.

Perception The processes by which people select, organize,

and interpret sensations.

Sensation and Perception

Sensation & Perception Processes

sensationSensation is defined as:

Irreducible elements from which perceptions are formed as experiences which are simpler and less meaningful than perceptions and uninfluenced by learning and other psychological processes such as emotion and motivation (Hebb, 1972; Scharf, 1975).

Problems of perception

No direct physical contact with the visual elements is required to appreciate there nature.

How do we form the impressions of the quantitative and qualitative aspects of external objects?

Does the real physical world actually exist independently of our experience? If so, how we can come to know its properties and how truth of that knowledge be determined?

Problems…

How percepts are constructed from the interaction of physical energy (light) and the perceiving organism.

Proximal and distal stimuli are different but our perceptions are generally accurate or veridical enough to adjust ourselves in the environment.

Some times percept have properties considerably different form proximal stimulus.

Components of perception

Distal stimulusDistal stimulus refers to a physical aspect of the

external environment, or the physical energy which comes from the eternal source. For example, object in the external environment such as, table, fan etc.

Proximal stimulusIt refers to the physical energy coming from the

external source strikes on the sensory receptors.

Components…

Input and outputInput refers to the sensation of stimulus and

output refers to behavior made in response to the input.

PerceptOut come of perception is known as percept.

Recognizing an object as flower would be an example of percept.

Difference between proximal and distal stimulus

Much of the light coming form distal source is scattered by molecules and lost before it reaches the receptors of the eye.

Resulting proximal image is much smaller, inverted relative to the distal stimulus

Proximal stimulus is partly under the control of observer’s head and eye movements.

Information in the form of electromagnetic energy is changed in the neural impulses (transduction).

Defining perception

According to Morgan and King, “perception is the way the world look (sounds, feels, tastes and smells too)”.

According to Zigher (1985), perception refers to the interpretation of sensory information, as a constructive and creative process which endows sensory experience with meaning.

Defining…Perception is a process by which

individuals organize and interpret their sensory impressions in order give meaning to their environment for making better adjustment with it.

Perception is a process by which we recognize and interpret or give meaning to raw material provided by sensory system with the help of other psychological processes such as, learning, memory, emotions and motivation.

Defining…

Perception is the process of creating an internal representation of the out side world (internal representation is a joint product of bottom up and top-down processing).

Perception is the interpretation of the information provided by sensory system.

Perception is active, selective and relatively more automatic higher mental process through which we experience or interpret our immediate surrounding.

Properties of perception

Perception is interpretation of physical energy or giving meaning to it.

In perception, registered stimuli by the senses are gathered and interpreted with the help of previous knowledge.

Perception combines aspect of both the outside world (the stimulus) and inner world (previous knowledge).

Properties …Perception is relatively more automatic

process, required less effort than other cognitive tasks, such as problem solving of decision making.

Perception is influenced by other psychological processes such as motivation and emotion.

Perception is an active mental process involves both top-down and bottom-up processing.

Concepts in perception

Physical- external or internal stimulus such as wave length, intensity etc.

Physiological- stimulation of sensory system: neural activity- excitation-inhibition; sensory modality: transduction

BehaviorSubjective experience

Perceptual OrganizationPerceptual ConstanciesDepth and DimensionPerceptual SetThe World of Illusions

Perception

Approaches to perception

StructuralismWilhelm Wundt and Edward Bradford

Titchner (1867-1927)Structuralisms emphasized on the study of

the structure of perception. Its goal was to uncover the simplest, most basic elements of conscious experience (bottom-up processing).

Constructivist Approach

Emphasized on the active nature of perceptual process. Influenced by empiricism.Proposed that the percept is more than the information

coming form stimulus.Some constructive processes occur within the observer.

These are mediating processes between physical world and its perception.

Our perception is a mental construction based on our cognitive strategies, past experiences, biases, expectations, motives, attention, and other personal characteristics

Direct perception approach (James J. Gibson, 1904-1979)

Stimulus contains important information necessary for perception

Past experiences are not importantPerception depends on the characteristics of

stimuli (subjective variables are not important)

It is also known as ecological approach because it focuses on the adaptive link between the perceiving organism to its physical environment.

Computational Approach (David Marr, 1945-1980)

Involves mathematically oriented analysis of certain aspects of visual perception derived form computer simulation and AI.

Accepts Gibson’s basic idea of direct perception but also proposes that perception of characteristics such as lines, edges, borders, contours, motion, and other discontinuity.

Beliefs of the information-processing approach

Information is processed in stagesInformation is processed seriallyThe nature of information changes stage to stageInformation processing is affected by several

factors (noise)It uses both bottom-up and top-down processingIt is a mediating process between input and output

Gestalt approach

(German: Gestalt - "shape" or "figure") Berlin School

Kurt Koffka, Max Wertheimer, and Wolfgang Köhler (students of Carl Stumpf) are the founder of this school. The 'Gestalt' or 'whole form' approach sought to define principles of perception -- seemingly innate mental laws which determined the way in which objects were perceived.

Gestalt: Basic idea

Operational principle of the brain is holistic, parallel, and analog, with self-organizing tendencies

“The whole is greater than the sum of the parts"

Opposed to structuralism and WundtGestalt effect refers to the form-forming

capability of our senses particularly visual sense.

Figure and groundProperties of figure groundFigures hold more memorable association than

the ground.Figures are seen as being in front of the ground.The ground is seen as uniformed material and

seems to extend behind the figure.The contour separating the figure from the

ground appears to belong to the figure.Compared to ground, perception of figure is

effortless

Field forces

Cohesive forcesRestraining forces∑ C = ∑ R = no perception (Ganzfeld)∑ C > ∑ R = perception∑ C < ∑ R = unclear or unstable perception

Laws of pragnanz

The fundamental principle of gestalt perception is the law of prägnanz (German for pithiness).

The physiological organization will always be good. Good refers to the simplest and most stable.

We tend to order our experience in a manner that is regular, orderly, symmetric, and simple.

Gestalt laws of perceptual organization

Gestalt psychologists modified Law of prägnanz and given laws which hypothetically allow us to predict the interpretation of sensation. These laws are called "gestalt laws".

Figure-ground

Drawings that one can perceive in different ways by reversing figure and ground.

Gestalt Psychology School of thought

rooted in the idea that the whole is different from the sum of its parts.

Perceptual Organization Reversible Figures

CamouflageImportance of contour

Proximity Seeing 3 pair of lines in A

Similarity Seeing columns of orange

and red dots in B

Continuity Seeing lines that connect

1 to 2 and 3 to 4 in C

Closure Seeing a horse in D

Perceptual Organization Gestalt Laws of Grouping

Gestalt Perceptual PsychologyLaws of Perceptual OrganizationLaw of Similarity

Gestalt Perceptual PsychologyLaws of Perceptual OrganizationLaw of Proximity (nearness)

General Perceptual PsychologyPrinciples of Perceptual OrganizationThe principle of common region

General Perceptual PsychologyPrinciples of Perceptual OrganizationThe principle of common region

General Perceptual PsychologyPrinciples of Perceptual OrganizationThe principle of connectedness

General Perceptual PsychologyPrinciples of Perceptual OrganizationThe principle of synchrony (objects that change

together are grouped together)

General Perceptual PsychologyPrinciples of Perceptual OrganizationRepetition Discrimination Task - groupings influence

perception and speed of search:

Perceptual SegregationFigure-ground segregation-We are primed to see a

figure in front of a backgroundSymmetry and perception of figure and ground

Perceptual SegregationFigure-ground segregation-We are primed to see a

figure in front of a backgroundArea size and perception of figure and ground

Perceptual SegregationFigure-ground segregation-We are primed to see a

figure in front of a backgroundOrientation and perception of figure and ground

Perceptual SegregationFigure-ground segregation-We are primed to see a

figure in front of a backgroundMeaningfulness and perception of figure and ground

Pattern recognition

Pattern recognition and attention prepare the raw sensory information for more complex mental process.

Pattern recognition allows us to perceive a form in a stimulus and attention is responsible for our more extensive processing of some information.

Pattern recognition is the identification of complex arrangement of sensory stimuli.

In pattern recognition raw information is organized and transformed by sensory process and compared with information in other memory storage.

Thus, pattern recognition involves realizing that a particular pattern is seen before.

Bottom up processing (Data driven)

• emphasizes importance of stimulus in PR.

• Information coming from the stimulus is enough to recognize the pattern.

• Recognition process in initiated by the parts of the pattern which serves as the basis for the recognition of whole.

Top down processing (conceptually driven)

Emphasizes that concept and high level of processing influence PR.

Our knowledge about the world help us identifying patterns.

The process of PR is initiated by a hypothesis about the whole leading to the identification of whole and the subsequent recognition of components.

Bottom up models of perception

How do we recognize patterns?

Do we identify an object because we have first recognize it’s components or do we recognize these part because we have first identified the object?

The problem that, whether the recognition process is initiated by the parts of the pattern or whether it is initiated by a hypothesis about the whole (hypothesis testing) is called prasing paradox.

A: Template Matching Theory

Templates are specific patterns that are stored in memory.

Stimulus is compared with a set of templates.

We recognize the stimulus as the template that matches most closely.

Stimulus must fit the template precisely.

Problems of TMT

If a number of templates match or come close (not one)-

We need further processing to sort out which template is most appropriate which will take much time than it actually takes.

It does not explain how perception works. with the development of technology our experiences change thus, how and when templates are created?

How different patterns are recognized as same despite the wide variation in the size, shape, orientation etc. (e.g. recognizing hand writing of different people).

It works for simple latter and simple objects.

B: Feature AnalysisFeature analysis model assumes that instead of

processing stimuli as whole units, we break them down into their components. We recognized those parts to infer what the whole represents.

There is physiological mechanism in retina and in the cortex. These are called feature detectors.

Some cells respond to boarders between light and dark called edge detectors.

Movement detectors are called bug detectors.Horizontal and vertical line detectors are also found

in the cortex.

1: Distinctive feature approachDiscrimination among letters is made on the basis of

small no of characteristics called distinctive features.

We store a list of feature components for each letter. E.g. Q has a round closed shape and a diagonal line.

Gibson (1969) demonstrated that people require long time to decide whether some letters are different from one another when the letter share large number of critical features.

For example, P and R are similar on a large number of critical features; and G and M are different from each other on a large number of critical features.

Differentiation between G and M takes less time as compared to differentiation between P and R.

In distinctive feature approach pattern recognition involves detecting specific important parts while in TMT emphasizes prototype and entire recognition of entire shape.

Problems of distinctive feature approach

Explain simple shape or features recognition such as letter recognition.

It does not explain physical relationships. For example, T and L are similar but they are recognize distinctly on the basis of relationship. For example, T has a vertical line supports a horizontal line in the middle. Where L has the vertical line rests at the side of the horizontal line.

It explains simple letter recognition but natural features, shapes are more complex. How can we recognize a horse?

2: The Computational Approach(David Marr (1982)

Images- Identification of object’s edges by combining intensity of the image

Primal sketch- edges are organized into abstract representation

2 ½ D sketch- primal sketch is converted into 2 ½ D sketch (contours, shade, rough depth)

3 D image- Describes shapes and their spatial organization of the object.

Geons (geometric icons) are simple 3D component shapes.

A limited number are stored in memory.

Geons are combined to identify essential contours of objects.

Perceptual OrganizationIdentifying Objects

Size Constancy The tendency to view an object as constant

in size despite changes in the size of the retinal image.

Shape Constancy The tendency to see an object as keeping its

form despite changes in orientation.

Perceptual Constancies

Perceptual Constancies The Ames Room

A specially-built room that makes people seem to change size as they move around in it

The room is not a rectangle, as viewers assume it is.

A single peephole prevents using binocular depth cues.

Even though these images cast shadows of different shapes, they still are seen as round.

Perceptual Constancies Shape Constancy

Size Constancy Tendency to view an object as constant in

size despite changes in the size of the retinal image.

Perceptual Constancies

http://www.psychologie.tu-dresden.de/i1/kaw/diverses%20Material/www.illusionworks.com/assets/images/constancy.jpg

Depth Perception: Binocular Depth

Cues

Binocular CuesBinocular Cues

Depth cues that require the use of both eyes

Enables people to see in three dimensions.

Retinal DisparityRetinal DisparityA binocular depth cue resulting from

slightly different images produced by the separation of the retinas in the left and right eye

Is most effective when the item is quite close to the person

Binocular Depth Cues: Finger Sausage

Retinal Disparity Text example page 189

Autostereograms

Retinal Disparity Demo

1. Roll a piece of scrap paper into a tube shape.2. Hold it to your right eye as if it were a telescope3. Look through the tube focusing on an object on a blank wall in front of you.4. Keeping both eyes open, hold your open left hand beside the tube…continue to focus on the object on the wall.5. The images should fuse and ….

ConvergenceA binocular depth cue related to the

tension in the eye muscles when the eyes track inward to focus on objects close to the viewer

The more tension in the eye muscle, the closer the object is

Works best at close distances

Monocular CuesMonocular CuesDepth cues that require the use of only

one eye

Monocular depth cues include:

1.relative size

2.relative motion

3.interposition

4.relative height

5.texture gradient

6.relative clarity

7.linear perspective

Components of Monocular Cues

Monocular Depth Cues 1. Relative Size1. Relative Size

Using the perceived size of a familiar object to determine depth

The larger the object appears, the closer the object is to the viewer

Monocular Depth Cues 2. Relative Motion2. Relative Motion

A person who is moving can determine depth by focusing on a distant object.

Objects further away than the object of focus will appear to move in the same direction as the subject is moving.

Objects closer than the object of focus will appear to move in the opposite direction.

Relative Motion Illustration

Monocular Depth Cues3. Interposition3. Interposition

Method of determining depth by noting that closer objects partially obstruct the more distant objects

Also called “overlap”

Monocular Depth Cues 4. Relative Height4. Relative Height

Method of determining depth by noting that distant objects appear higher in your field of vision than do closer objects

Monocular Depth Cues

5. Texture Gradient5. Texture GradientMethod of determining depth by noting that distant objects

have a smoother texture than nearby objects

Can see individual blades of hay, but in theDistance, the hay seems to have a smootherTexture.

Monocular Depth Cues 6. Relative Clarity6. Relative Clarity

Method of determining depth by noting that distant objects are less clear than nearby objects

Tends to work outdoors

Paris Street: A Rainy Day by Gustave Caillebotte

Monocular Depth Cues7. Linear Perspective7. Linear Perspective

Method of determining depth by noting that parallel lines appear to converge in the distance

The lines appears to eventually merge on the horizon.

As parallel lines become more distant from us, they appear to get closer together - like the sides of the gray bit at left.  Their apparent closeness is therefore a cue to their relative distance from us.

Devised by Eleanor Gibson and Richard Walk to test depth perception in infants and animals.

Provides visual illusion of a cliff.

Caregiver stands across the gap.

Babies are not afraid until about the age they can crawl.

Depth and Dimension 8.The Visual Cliff8.The Visual Cliff

What is seen in the center figures depends on the order in which one looks at the figures: If scanned from the left, a man’s face is seen. If scanned from the right, a woman’s figure is seen.

Perceptual Set

The same physical stimulus can be interpreted differently depending on perceptual set, e.g., context effects.

When is the middle character the letter B and when is it the number 13?

Perceptual Set Context Effects

Illusion in which the perceived length of a line is altered by the position of other lines that enclose it

The World of Illusions The Müller-Lyer Illusion

Illusion in which the perceived line length is affected by linear perspective cues.

Side lines seem to converge

Top line seems farther away

But the retinal images of the red lines are equal.

The World of IllusionsThe Ponzo Illusion

The ganzfield procedureResearchers disagree about the reliability of

studies done to replicate the ganzfield test. Visit www.randi.org/ for information about

the James Randi Educational Foundation’s million-dollar paranormal challenge.

The Continuing Controversy