Perception - Cognitive Processes - Lecture Slides, Slides of Brain and Cognitive Science

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Perception

Object Recognition

 Two stages:

 Early phase – shapes and objects are extracted from background.  Later phase – shapes and objects are categorized, recognized, named.

Tests for Apperceptive

Agnosia

Some patients would have trouble drawing this chair due to the missing contours.

Some patients would have trouble recognizing a chair from this perspective.

Tests for Associative Agnosia

The subject can copy the anchor accurately (as shown) but then cannot tell you what it is.

The Eye

Later Visual Processing

 Neural pathways from the eyes to the visual cortex split at the optic chiasm.  Info from the left visual field goes to the right hemisphere.  Info from the right visual field goes to the left hemisphere.

 Two pathways from the visual cortex:

 “Where” pathway  “What” pathway

Pathways Forward

Information Coding

 On-off cells in LGN feed into edge and bar detectors in the visual cortex.

 Edge detectors – respond positively to light on one side of a line, negatively on the other side of the line.

 Bar detectors – responds maximally to a bar of light covering its center.

Edge & Bar Detectors (Cont.)

Computer Edge Detection

Depth Perception

 Our eyes turn a three-dimensional world into a two-dimensional image on the retina.

 Our cortex turns that two-dimensional image back into three-dimensions (depth).

 Cues are used to infer distance.

 Cues must be learned through experience.  Depth cues in art

Depth Cues

Size Constancy is Mental

The same photo