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Perception - PowerPoint PPT Presentation

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Perception. The set of processes that organize information in the sensory image and interpret that information as having been produced by objects or events in the external world Role is to make sense of sensations What is perceived

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  • The set of processes that organize information in the sensory image and interpret that information as having been produced by objects or events in the external world

  • Role is to make sense of sensations

  • What is perceived

  • The overall process of comprehending objects and events in the environment


  • 3 stages

    • Sensation-conversion of physical energy in to neural code

    • Perceptual organization-internal perception of an object is formed and a percept of the external stimulus is developed. Working representation of the perceivers external environment ex(vision-seize, shape, movement, distance)

    • Identification/recognition-assigns meaning to percepts (ex. Circles become coins, balls clocks etc.)


  • Retinal image 2 dimensional

  • Distal

    • Physical objects in the world

  • Proximal

    • Optical image on the retina

  • Ambiguity

    • Perceptual object that may have more than one interpretation

  • Illusions

    • Perceptual systems actually deceive you into experiencing a stimulus pattern in a manner that is a demonstratably incorrect









Study of Perception

  • Helmholtz (1866)-nurture

    • Using prior knowledge

  • Unconscious inferences

    • Perception that occurs outside of conscious awareness

  • Analytic stage-break physical world down

  • Synthetic stage-integrate and synthesize

Study of Perception

  • Gestalt-Koffka(1935)/Kohler (1947)/ Wertheimer (1923)

    • Viewed as organized, structured wholes

    • Whole is more than the sum of its parts

Gestalt principals



Study of Perception

  • Theory of Ecological options Gibson+Gibson (1966+1979)

    • Focused on the properties of external stimuli

    • Perceiver as an explorer of the environment

Attentional Processes

  • Attention-state of focused awareness on a subset of the available perceptual information

Attentional Processes

  • Goal directed selection

    • Choices you make about objects to which you’d like to attend

Attentional Processes

  • Stimulus-driven capture

    • Features of stimulus-objects in the environment, capture your attention

Attentional Processes

  • Filter Theory (Broadbent 1958)

    • Mind has limited capacity to take in information and the selection occurs early on in the process before the input’s meaning is accessed

    • Dichotic listening

      • Different auditory stimulus is simultaneously presented in each ear



Attentional Processes

  • Preattentive Processes

    • Processing of sensory information that precedes attention to specific objects

    • Allows guided search

Organizational Processes

  • Divides stimuli into figures

    • Figures-object like regions of the visual field that are distinguished from background

    • Ground-backdrop or background areas of the visual field against which figures stick out

Organizational Processes

  • Illusory contours

    • Contours perceived in a figure when no contours are present

Kaniza Triangle Effect


Organizational Processes

  • Closure-makes you see incomplete figures as complete, balanced, symmetrical



Organizational Processes

  • Law of Proximity

    • Law of grouping states the nearest or most proximal, elements are grouped together

Law of Proximity


Organizational Processes

  • Law of similarity

    • Law of grouping states: similar elements are grouped together



Organizational Processes

  • Law of common fate

    • Law of grouping states: elements moving in same direction at the same rate are grouped together


  • Fixation-glance at something becomes fixed in mind

  • Spatial+temporal integration

    • Fixed locations in different moments for seeing what is around you

Fixed Motion



  • Changing of size

  • Induced motion

    • An illusion in which a stationary point of light with in a moving reference frame is seen as moving +the reference frame is seen as stationary

Motion (Phi phenomenon)

  • Apparent motion-movement illusion in which one or more stationary lights going on and off in succession are perceived as a single moving light

Phi Phenomenon


Depth Perception

  • Depth-distance from an object

Depth Perception

  • Depth cues

    • Binocular

      • 2 eyes

      • Retinal disparity-displacement between the horizontal positions of corresponding images in the two eyes

Depth Perception

  • Depth cues

    • Convergence

      • Degree to which eyes turn inward to fixate on an object

Depth Perception

  • Relative motion parallax

    • Depth, relative distances of object from a viewer determine the amount + direction of their relative motion in the retinal image

Depth Perception

  • Pictorial cues

    • Depth perception using one eye

    • Interposition or occlusion

      • Blocking out an object (one is in front of another)

      • Shadows ex. Person inside window

    • Size/distance relation

      • Closest projects largest size

        • Railroad example

Ponzo Illusion

Depth Perception

  • Perceptual constancy

    • The ability to retain an unchanged percept of an object despite various retinal images ex. Person moving round-close, back etc.

Depth Perception

  • Size constancy

    • The ability to perceive the true size of an object despite variations in the size of the retinal image

    • Prior knowledge

Ames Box


Depth Perception

  • Shape constancy

    • Ability to perceive the true shape of an object despite variation of size of retinal image

Depth Perception

  • Orientation constancy

    • Ability to perceive the actual orientation of objects in the real world despite their varying orientation in the retinal image

    • Whit help from inner ear

Depth Perception

  • Lightness constancy

    • The tendency to perceive the whiteness, grayness or blackness of objects as constant across changing levels of illumination


  • Less to more abstract


Information passed down from experience

Abstract to concrete

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