Describe the concept of perceptual organisation. Explain how the Gestalt laws and other theories attempt to account for object perception

Perceptual Organization

 Perceptual segregation:

  • Separating visual input into individual objects
  • Thought to occur before object recognition

Gestalt Psychology

  • The law of pragnanz – of several geometrically possible organisations that one will actually occur which possesses the best, simplest and most stable shape
  • Configural superiority effect – the beneficial effect (in terms of processing time) of organization
  • Gestalt laws of perceptual organization – law of proximity, similarity, good continuation, and closure

Viewpoint Theories

  • Viewpoint-invariant theories suggest that object recognition is based on structural information, such as individual parts, allowing for recognition to take place regardless of the object’s viewpoint
  • Viewpoint-dependent theories suggest object recognition is affected by the viewpoint at which it is seen, implying that objects seen in novel viewpoints reduce the accuracy and speed of object identification

Marr’s Theory

  • Primal sketch – 2D description of light-intensity changes (edges, contours, blobs)
  • 2 ½ D sketch – incorporates depth and orientation of surfaces (shading, texture, motion, binocular disparity)
  • 3D model representation – 3D object shape

Biederman’s Recognition by Components Theory

  • Objects consist of combinations of geons – geometric shapes (36 basic shapes)

Describe multi-stage information processing models of object perception and explain how disorders of object perception such as visual agnosia and apperceptive agnosia support these models

  • The multi-stage information processing models of object perception – different pathways of visual processing
    • Inferno-temporal cortex – Parvocellular Pathway – ventral ‘what’ stream
    • Parietal Cortex – Magnocellular Pathway – dorsal ‘how’ stream
    • Primary Visual Cortex – ‘what’ and ‘where’ stream
  • Visual Agnosia – loss of object recognition
    • Apperceptive agnosia – deficit in object perception creating an inability to understand the significance of objects
    • Associative agnosia – the inability to understand the significance of objects, however, this time the deficit is in semantic memory o Both of these agnosias can affect the pathway to object recognition
    • Prosopagnosia – a difficulty in recognizing faces
  • Object recognition is a complex task which involves several different areas of the brain – if one is damaged then object recognition can be impaired
  • When object agnosia occurs form a lesion in the dominant hemisphere, there is often a profound associated language disturbance, including loss of word meaning

Describe the process of face recognition and give arguments for and against the hypothesis that we have special processes and brain areas dedicated to face processing

Holistic (configural) Face Processing

  • Face-inversion effect – inverted faces are disproportionately harder to recognize than upright faces relative to objects (Yin, 1969)

–     Fusiform face area – an area in the inferotemporal cortex that responds more to upright faces than inverted face and objects o Generally more receptive to faces than to objects – however other brain regions also selective to faces (occipital area, temporal sulcus)

  • Part-whole effect – memory for a face-part more accurate when presented within the whole face (Farah, 1994)
  • Composite effect – perceiving half a face is more difficult when it appears against a different complementary half (Richler et al., 2011)

Prosopagnosia

  • Multiple reasons why face processing might be impaired: – Brain damage to face-processing region

–     Face recognition might just be harder because it involved making finer distinctions – a double dissociation could help disambiguate these possibilities

  • Impaired holistic processing – restricted perceptual field (Van Belle et al., 2011)

Compare and contrast Kosslyn’s and Pylyshyn’s explanation of visual imagery. Describe the evidence that has been used to support each model

Kosslyn’s Perceptual Anticipation Theory

  • Visual images are depictive representations
    • Like pictures or drawings of objects that can be arranged in space
    • Formed in topographically organized brain areas forming the visual buffer o Early visual cortex (V1) o Secondary visual cortex (V2)
  • Predicts that perception and imagery should influence each other

Pylyshyn’s Propositional Theory

  • Imagery is only tacit propositional knowledge
    • Generally unconscious, stored knowledge about object
    • The nature of tacit knowledge is not very well defined Evidence to Support
  • Overlapping brain regions for imagery and perception

Describe, with examples, Gibson’s notion of direct perception, information pickup and affordances. Explain how these ideas can be used to understand visuallyguided action

Gibson’s Direct Perception

  • There is more to perception than object identification
    • Perception and action are closely intertwined
    • An ecological approach in his direct theory of perception
  • Information pickup from the ambient optic array
    • The pattern of light reaching the eye
    • Provides unambiguous information about object layout
    • This occurs without much information
  • Affordances
    • Potential used of objects
    • Perceived directly

Describe the special features of biological motion. Outline evidence for and against the role of the mirror neuron system in detection of biological motion, imitation and interpreting intent

Biological Motion

  • Spontaneous, automatic, and innate
  • Superior temporal and premotor frontal areas involved in perception of biological motion

Imitation and Mirror Neurons

 Mirror neuron system

  • Formed of neuron activated when animals perform an action and when they observe another performing the same action
  • Facilitates imitation and understanding others’ actions
  • Regions that respond to performing an action or watching others perform it – ventral premotor cortex, anterior intraparietal cortex, and superior intraparietal cortex

Evaluation

 Strengths:

  • An impressive ability
  • Specific brain regions
  • Evidence of a mirror neuron system  Limitations:
  • Relatively little is known about how bottom-up and top-down processes interact
  • Claims of the mirror neuron system are overstated
  • The human mirror neuron system has yet to be detected on the neuronal level
  • Mirror neurons are unlikely to account for all biological motion detection and the definition is not specified