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8/8/2019 Hout Perception

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PERCEPTION 1

PERCEPTION

Involves taking in of information, through the activity of our

sense organs responding to external stimulation, followed bythe processing of that information to make sense of what wesee, hear, smell, taste and touchA discernment of the nature of objects, their position, shape,size, distance, scent, taste, texture and their meaningResult when we interpret, organize and elaborate on the rawmaterials of sensation

Five perceptual systems

1. Visual Seeing2. Auditory Listening3. Haptic Touching4. Savor perceptual

system

Smelling and tasting

5. Basic orientationalperceptual system

Balance, posture and position ofthe body and its movements

SENSATION VS PERCEPTION

Sensation is the firstawareness of some outsidestimulus

Perception is usually thechanged, biased, colored ordistorted by our unique set ofexperiences the personalinterpretations of the realworld

Structuralists vs Gestalt Psychologists

Structuralists: you addtogether hundreds of basicelements to form complexperceptions. You can workbackward to break downperceptions into smaller andsmaller units or elements

Gestalt Psychologists:our brains follow a set orrules that specify howindividual elements were tobe organized into ameaningful pattern

Gestalt Psychologists won the debatePersonal perceptual experiencesForming perceptions involved more than adding and

combining elements. Our brains actually did follow a set ofrules.

THRESHOLD

Least amount that can elicit a responsePoint in above in which a stimulus is perceived and belowwhich it is not perceivedDetermines when we first become aware of a stimulus

Gustav Fechner defined absolute threshold as thesmallest amount of stimulus energy that can be observedunder the same conditionsHowever, he found out that individuals threshold was notabsolute and in fact, differed depending on the subjectsalertness and test situation.

Redefinition ofABSOLUTE THRESHOLD : intensity levelof a stimulus such that a person will have a 50% chance ofdetecting it

Subliminal stimulus

Has an intensity that gives the person a less than 50%chance of detecting it

JUST NOTICEABLE DIFFERENCE (JND)

JND refers to the smallest increase or decrease in theintensity of a stimulus that a person is able to detect

Webers Law

The increase in intensity of a stimulus needed to produce aJND grows in proportion to the intensity of the initial stimulus

Perception

100% chance ofhearing messageAbsolute threshold:

50% chance ofhearing message

Subliminal stimulus:0-49% chance ofhearing message

Increasing intensity

Higher intensities: you need a largerdifference to detect JND

Lower intensities: you need onlysmall differences to detect JND


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PERCEPTION 2

ORGANIZATIONAL RULESIdentified by Gestalt PsychologistsSpecified how our brains combine and organize individualpieces or elements into a meaningful perception

Figure-groundWe automatically distinguish between a subject and its

background. The figure will stand out more than thebackground

SimilarityWe tend to organize stimuli that appear similar, even if there isno relationship.

ClosureWe tend to "finish" items to make a shape, even if those partswe "finish" aren't actually drawn in.

ProximityWhen processing items, we tend to group them based on howclose they are to other objects. In a series of dots, instead ofseeing them as individual dots, we might see them as onegroup of four, one group of five and so on if there is spacebetween them.

Simplicity/PragnanzWe initially see things in the simplest way possible. Afterfurther review, we may see things more clearly. Think any typeof visual illusion that may have two ways to see it

ContinuityWe tend to see things in a constant flow, even if they do notgo together. We look for constancy in most things.

PERCEPTUAL CONSTANCYRefers to our tendency to perceive sizes, shapes, brightness,and colors as remaining the same even though their physicalcharacteristics are constantly changing

Size constancyOur tendency to perceive objects as remaining the same sizeeven when their images on the retina are continually growing

or shrinking

Shape constancyOur tendency to perceive an object as retaining its same shapeeven though when you view it from different angels its shapeis continually changing its image on the retina

Brightness and color constancyBrightness constancy: Our tendency to perceive brightness asremaining the same in changing illuminationColor constancy: Our tendency to perceive objects asremaining stable despite differences in lighting


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PERCEPTION 3

DEPTH PERCEPTIONRefers to the ability of your eye and brain to add a thirddimension, depth, to all visual perceptions, even thoughimages projected on the retina are only two dimensions, heightand width.

MONOCULAR CUES

Produced by signals from a single eye. Monocular cues mostcommonly arise from the way objects are arranged in theenvironment.

Linear PerspectiveResults as parallel lines come together, or converge, in thedistance

Relative sizeResults when we expect two objects to be the same size andthey are not. In that case, the larger of the two objects willappear closer and the smaller will appear farther away

InterpositionWhen images overlap, they appear to be of different depths,with the figure at the front being the closest

Light and shadowBrightly lit objects appear closer, while objects in shadowsappear farther away

Texture GradientAreas with sharp, detailed texture are interpreted as beingcloser, and those with less sharpness and poorer detail areperceived as more distant

Atmospheric PerspectiveWe perceive clearer objects as being nearer and perceive hazyor cloudy objects as being farther away

Motion parallaxWe perceive objects that appear to be moving at high speed ascloser to us than those moving more slowly or appearingstationary

BIN OCULAR CUESProduced by signals from both eyes. Binocular cues operatebecause our brain receives two views of the visual world, onefrom each eye.

ConvergencePerception based on signals sent from muscles that turn theeyes. To focus on near or approaching objects, these musclesturn the eyes inward, toward the nose. The brain uses thesignals sent by these muscles to determine the distance of theobject


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PERCEPTION 4

Retinal disparityPerception that depends on the distance between the eyes.Because of their different positions, each eye receives a slightlydifferent image. The difference between the right and left eyesimage is the retinal disparity. The brain interprets a largeretinal disparity to mean a close object, and a small retinal

disparity to mean a distant object

ILLUSION

An optical illusion is characterized by visually perceivedimages that, at least in common sense terms, are deceptive ormisleading.

Ambiguous illusionsPictures or objects that elicit a perceptual 'switch ' betweenthe alternative interpretations. The Necker cube is a wellknown example; another instance is the Rubin vase.

Distorting illusionsCharacterized by distortions of size, length, or curvature. Astriking example is the Caf wall illusion. Another example isthe famous Mueller-Lyer illusion.

Paradox illusionsGenerated by objects that are paradoxical or impossible ,such as the Penrose triangle or impossible staircases seen, forexample, in M. C. Escher'sAscending and Descending andWaterfall.

HallucinationsFictional illusion of objects that are genuinely not there to allbut a single observer, such as those induced by schizophreniaor a hallucinogenic substance.

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