Perception for object recognition and action

Question 1

Functions of the dorsal stream

Answer 1

 Perception for action - How do I interact with what I see?

 Eye hand coordination and orientation in space

Question 2

Functions of the ventral stream

Answer 2

 Perception for identification – What do I see?

 Form and colour presentation and object recognition

Question 3

Reconciliation of constructivist and ecological approach

Answer 3

 Dorsal stream often works without conscious perception (ecological)
 Ventral stream is a higher system whose output is conscious (constructivist)

Question 4

What is Riddoch and Humphreys (2001) model of visual object recognition?

Answer 4

Groups elements into higher order units to recognise objects (Gestalt Principle)

Question 5

What are Gestalt’s 5 laws of perception?

Answer 5

 law of proximity - Visual elements are more likely to be grouped together when closer in proximity
 law of similarity - Elements that share visual attributes are more likely to be grouped together
 law of good continuation - Edges are grouped together to avoid changes or interruptions
 law of closure- Missing parts are filled in, important for recognising objects partly occluded
 law of common fate - Elements that move together tend to be grouped together

Question 6

What is the neuropsychological evidence for Gestalt grouping?

Answer 6

Integrative agnosia patient (has difficulties integrating parts in a whole picture) HJA unable to recognise pictures of objects but can describe them in detail

Question 7

What is object constancy and how does it work?

Answer 7

 Recognition of objects at different viewpoint and in different lighting conditions
 Information about object stores in LTM

Question 8

How does object constancy work in the brain?

Answer 8

 Marr and Nishihara (1978) - objects can be decomposed into segments and the axes of these cones are extracted and maintained in memory making it easy to recognise object regardless of view point
 Bierderman (1987) – achieved by matching parts of an object to stored representations in memory

Question 9

Which visual cues are used by the dorsal stream coding object properties (Norman, 2002)?

Answer 9

 Binocular vision

 Motion parallax

Question 10

Neuropsychological evidence for understanding an objects function

Answer 10

 Visual agnosia patients that cannot describe an object or its function can still produce the motor action appropriate to the object (phantomiming)