Being suspicious of suspicious coincidences: The case of learning subordinate word meanings.

How do learners acquire subordinate terms (such as Dalmatian) and overcome the bias that words have basic-level meanings (such as dog)? Xu and Tenenbaum [Xu, F., & Tenenbaum, J. B. (2007a). Word learning as Bayesian inference. Psychological Review, 114(2), 245-272] found that both children and adults can learn the subordinate meaning of a novel word when it is used ostensively to label multiple exemplars: learners appear to reason about sampling statistics, detecting the suspicious coincidence that, e.g., a random sample of dogs all happen to be Dalmatians. Crucially though, their experimental support did not come from cross-situational ostensive labeling contexts, but from single instances that presented all exemplars at once and included a co-present test array that likely highlighted the relevant semantic contrast. Here we find that adults do not use suspicious coincidences during cross-situational word learning. We only find effects of suspicious coincidences in adults under specific testing conditions similar to those used by Xu and Tenenbaum. We find that adults show a basic-level meaning preference even after encountering five subordinate-level exemplars cross-situationally, even when the first three exemplars were presented simultaneously and labeled ostensively. Instead, participants arrived at subordinate meanings only within settings that highlighted the relevant semantic contrast, i.e., when the target words had referents that belonged to the same basic-level category (e.g., two words referring to dogs, with one referring to Dalmatians and the other to non-Dalmatian dogs). Our findings are consistent with a "semantic contrast" account of word learning, in which learners evaluate which semantic contrasts are relevant in the local learning context and use that information to constrain word meaning.