Figure 
shows the results of Experiment 3 over 10
runs of the network.
The noun-like
categories that were organized by an equally restricted range of
variation on all four sensory dimensions were learned more
rapidly than the adjective-like categories in which the range of
variation on some dimensions was wide and on others narrow
(
).
In other words, evenly compact categories are more rapidly learned
than elongated ones, a difference which again favors the basic-level
nouns children learn early over the dimensional adjectives
that they learn later. We also assessed the association of noun
and adjective outputs with the two different linguistic inputs by
measuring within- and between-category errors. At the start of
learning, within category errors were at chance; the proportions
of all errors (above threshold responses) that were within
syntactic category were .45 and .53 for nouns and adjective
respectively. After 2000 trials, the proportions of within-category
errors were .85 for both nouns and adjectives. Given
that the input specified two categories, this result is not
surprising but it does demonstrate again the learning of word-word
associations and their potential role in generating
structured patterns of errors.
: Experiment 3: Category Compactness.
Performance is the proportion of test items for which the highest
overt response was correct.
Responses are averaged over 10 separate runs of the network.
