2.3.2.1.2 Taxonomic constraint
Related to the whole object constraint is the taxonomic constraint, which is that “labels
refer to objects of the same kind rather than to objects that are thematically related”
(Markman, 1990, p.59). Thematically related entities include those that fall into “spatial,
causal, temporal, or other relations” such as a dog and its bone, a dog and the tree that it
is under, a dog and the person who is petting it, and so on. One important aspect of this
proposal is that it is intended to be special to word learning. In a task that does not involve
language, children are highly sensitive to thematic relations, for example, they will put a
dog and a bone together when asked to sort objects into different piles (Markman, 1981).
Markman’s hypothesis is that this “taxonomic constraint” forces children to override this
bias and attend to taxonomies (such as the kind DOG) when faced with the task of
inferring the meaning of a new word.
Markman and Hutchinson (1984) present a set of studies that directly test this hypothesis.
In one experiment, 2- and 3- year-olds were randomly assigned to one of two conditions.
In the no word condition, they were shown a target picture (e.g., a dog) along with two
other pictures, one of the same category (e.g. another dog) and one that was thematically
related (e.g. a bone) and told: “See this ? Can you find another one?” In the novel word
condition, children were shown the same pictures and told: “ See this dax. Can you find
another dax?” They found that children in the no word condition tended to choose the
thematic associate, while children in the novel word condition tended to choose the object
that belongs to the same category as the target. This suggests that the taxonomic
assumption is special to word learning.
Nevertheless, the taxonomic assumption, has been widely criticised. Bavin, Ng, Brimmell
and Gabriel (1993) have reported that 3 year olds who are acquiring Greek and Chinese
do not behave in the same way as children learning English when given Markman’s and
Hutchinson’s task. Also, Ralli and Dockrell (1995) showed that children’s performance
in the Markman’s and Hutchinson’s task changes when the context of presentation is
modified.
In general, these constraints (taxonomic constraint and whole object constraint) are posited
to explain the acquisition of words that refer to kinds of whole objects (e.g. dog), but the
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