PERCEPTION

GESTALT PSYCHOLOGY AND PERCEPTUAL ORGANIZATION
Form perception
Grouping

Gestalt Laws of Perception
~ Proximity
~ Similarity
~ Continuity
~ Closure
~ Part-whole relationship
~ common fate

An evaluation of the Gestalt contribution.
~ A major philosophical influence on Gestalt psychology was phenomenology.
~ “there seems to be a single starting point for psychology, exactly as for all the other sciences: the world as we find it, naively and uncertainly”.

~ Navon’s work on global and local concepts.


Depth perception
~ non-pictorial (primary) cues
* retinal disparity
* stereopsis
* accomodation
* convergence
~ Pictorial (secondary) cues
• relative size
• relative brightness
• superimposition (overlap)
• linear perspective
• aerial perspective
• height in the horizontal plane
• light and shadow
• texture gradient
• motion parallax

Perceptual Constancy
• size constancy
• location constancy
• brightness constancy
• colour constancy


Illusions
• distortions(geometric illusions)
o eg: Ponzo illusion, Poggendorf illusion, Muller-Lyer illusion, horizontal-vertical illusion,Titchener’s circles,twisted card illusion


• ambiguous or reverible figures
o eg:Necker cube, Boring’s Old/Young Woman


• paradoxical figures or impossible objects
o eg:Penrose Impossible Triangle, The Devil’s Pitchfork, M.C. Escher’s Relativity.


• Fictions
o Eg:white triangle, the curved subjective contours, lines of different orientation producing a subjective contour.

Illusions of movement
Examples:
• The autokinetic effect
• Stroboscopic motion
• The Phi Phenomenon
• Induced movement
• Motion after effects

Perception of Real movement
• The importance of eye working and brain.
• Configurational change



THEORIES OF VISUAL PERCEPTION:
• Direct (bottom-up/data driven) or “ecological as said by Bruce & Green”
• Indirect (top-down/conceptually driven) or “traditional”
• Nature (nativists approach)
• Nurture (empiricists approach)



GREGORY’S CONSTRUCTIVIST THEORY
“Perception is not determined simply by stimulus patterns. Rather, it is a dynamic searching for the best interpretation of the available data … [which] involves going beyond the immediately given evidence of the senses” _Gregory (1966)

Gregory’s theory and perceptual constancies keeping in view the concepts of low-level knowledge (sensory inputs to the retina)and high-level knowledge (expectations based on past experience), Gregory argues that perception must be an indirect process involving a construction based on physical sources of energy.

~ Gregory’s theory and Perceptual set:
• selector
• interpreter.

Followings are the inputs to such set and the output is perceived by the selector and interpreter.
• motivation
• emotion
• values
• beliefs
• cognitive style
• context and expectations


GIBSON’S THEORY OF DIRECT PERCEPTION:
~ optic flow patterns
~ texture gradients
~ affordances



NOTE: you must understand different theories in order to know the determinants of percetion.

__________________
~A Philosophy Freak~