Learned Categorical Perception in Neural Nets: Implications for Symbol Grounding

Harnad, Stevan and Hanson, Stephen J. and Lubin, Joseph (1995) Learned Categorical Perception in Neural Nets: Implications for Symbol Grounding. [Book Chapter]

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After people learn to sort objects into categories they see them differently. Members of the same category look more alike and members of different categories look more different. This phenomenon of within-category compression and between-category separation in similarity space is called categorical perception (CP). It is exhibited by human subjects, animals and neural net models. In backpropagation nets trained first to auto-associate 12 stimuli varying along a one-dimensional continuum and then to sort them into 3 categories, CP arises as a natural side-effect because of four factors: (1) Maximal interstimulus separation in hidden-unit space during auto-association learning, (2) movement toward linear separability during categorization learning, (3) inverse-distance repulsive force exerted by the between-category boundary, and (4) the modulating effects of input iconicity, especially in interpolating CP to untrained regions of the continuum. Once similarity space has been "warped" in this way, the compressed and separated "chunks" have symbolic labels which could then be combined into symbol strings that constitute propositions about objects. The meanings of such symbolic representations would be "grounded" in the system's capacity to pick out from their sensory projections the object categories that the propositions were about.

Item Type:Book Chapter
Keywords:Neural nets, symbol grounding, categorical perception
Subjects:Computer Science > Dynamical Systems
Computer Science > Neural Nets
Psychology > Perceptual Cognitive Psychology
ID Code:1596
Deposited By:Harnad, Stevan
Deposited On:19 Jun 2001
Last Modified:11 Mar 2011 08:54

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