Paper on lexical acquisition

[Michael Gasser]

FTP-host: cs.indiana.edu (129.79.254.191)
FTP-filename: /pub/techreports/TR382.ps.Z

The following report is available in compressed postscript form by
anonymous ftp from the site given above (note: NOT neuroprose).  The
paper is 23 pages long.  If you have trouble printing it out, please
contact me.

Michael Gasser
gasser at cs.indiana.edu

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		Learning Noun and Adjective Meanings:
		       A Connectionist Account

			    Michael Gasser
	     Computer Science and Linguistics Departments

			    Linda B. Smith
			Psychology Department

			  Indiana University

			       Abstract

   Why do children learn nouns such as {\it cup\/} faster than
dimensional adjectives such as {\it big\/}?  Most explanations of this
well-known phenomenon rely on prior knowledge in the child of the
noun-adjective distinction or on the logical priority of nouns as the
arguments of predicates.  In this paper we examine an alternative
account, one which seeks to explain the relative ease of nouns over
adjectives in terms of the response of the learner to various
properties of the semantic categories to be learned and of the word
learning task itself.  We isolate four such properties: the relative
size and the relative compactness of the regions in representational
space associated with the categories, the presence or absence of
lexical dimensions in the linguistic context of a word ({\it what
color is it?\/} vs. {\it what is it?\/}), and the number of words of a
particular type to be learned.  In a set of five experiments, we
trained a simple connectionist categorization device to label input
objects, in particular linguistic contexts, as nouns or adjectives.
We show that, for the network, the first three of the above properties
favor the more rapid learning of nouns, while the fourth favors the
more rapid learning of adjectives.  Our experiments demonstrate that
the advantage for nouns over adjectives does not require prior
knowledge of the distinction between nouns and adjectives and suggest
that this distinction may instead emerge as the child learns to
associate the different properties of noun and adjective categories
with the different morphosyntactic contexts which elicit them.