General perception revision

  • Created by: freya_bc
  • Created on: 10-01-17 14:51

Biederman's (1987) RBC

Allows more complex forms that cylinders- objects= basic shapes/components called GEONS
Small range if geons can combine to represent objects just like phonemes for words
Non-accidental properties in primal sketch sufficient to define 3D component represenations- regularities in image= regularities in world 


CURVATURE: points on a curve
PARALLEL: sets of points in parallel
CO-TERMINATION: edges terminating at common point 
SYMMETRY: vs asymmetry
CO-LINEARITY: points in a straight line 

If things have these properties they are more likely to be grouped together 

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Biederman's (1987) RBC

From geons to objects

Objects- relationships between geons 
35 geons lead to 30k discriminable objects- object recognition only needs edges
Not impaired by changes in colour, texture or fine detail (Biederman and Ju, 1988)
Pull out important bits of image to build the basic shapes 

Geons= blocks, cylinders, spheres, arcs, wedges 

Providing concavities of a contour are visible, mechanisms allowing the missing parts of a contour can be restored. Disrupted when these parts are missing. Normally considered REDUNDANCY in image- complex objects can still be ID'd when some geosn missing 

Able to recog objects based on invariant properties, concavities and redundant information e.g. could recognise a giraffe form its neck alone- don't need to see any of the other features 

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Perception and action

Milner and Goodale (1995) 
Info from primary visual cortex diverges into two anatomical streams 
Visual info= processed in OCCIPITAL LOBE > dorsal > posterior parietal cortex
OCCIPITAL LOBE > ventral > inferior temporal cortex 

DORSAL- Dorsal- vision for action
e.g. should be immune to illusions because it needs to provide accurate info about the world- omputes how you can interact with something/where it is/size/shape/what can do with it 

VENTRAL- ventral- vision for identification 
e.g. illusions tap the ventral stream- conscious visual perception- aware of what things look like, less aware of calculations you are making of how you can scale it to pick it up 

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Affordances- Gibson

Meaning is not necessary to interact with envi- something in image to tell you how to use it even if don't know what it is 

Questions role for LTM in using objects

All potentail uses of object directly perceivable (without t-d knowledge)- animal/envi are directly interlinked e.g. ladder affords climbing, chair affords sitting 

Some have multiple affordances e.g. glass can hold liquid or trap a spider 

Affordance of surface/object= what it can offer the animal e.g. log-human= sit, frog= hop on 

Shape of hammer show you anthropormetrically/ergoonomically where to pick it up, same with door handles etc e.g. indicated by height/shape 

Learn which affordancs will satsify life goals 

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How do perceivers pick up invariant info from visual wordl? 

Gibson  proposed resonance- analogous to workings or radio.


Animals pick up info automatically/effortless providing they are attuned to that info e.g. hopping affordances not perceived by a human 

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Top-down approach

HELMHOLTZ (1821-1894)
Inadequate info provided by senses is augmented (added to) by unconscious inference.
1. Perception is an active and constructive process
2. End-product of presented stimulus and internal factors (hypotheses/expectations/motivations)
3. Errors will occur in perception because of the hypotheses influence 

GREGORY (1923-2010)
Elaborated theory of perception as INFERENCE
'Not just determied simply by stimulus patterns, is dynamic searching for best interpretation of available data...going beyond immediately given evidence of senses' 
Intepretative/indriect nature of visual perception demonstrated by PERCEPTUAL CONSTANCY and ILLUSIONS

PERCPETUAL CONSTANCY- shape constancy, orientation constancy, location constancy
VISUAL ILLUSIONS- distortions, ambiguous figures, paradoxial figures, fictions 

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