The role of word learning in the development of dimensional attention

Previous work shows that young children focus on holistic (or overall) similarity and older children focus on dimensional similarity (selectively attending to one property to the exclusion of others). Research on early word learning, however, suggests that process of learning new words trains attention towards category-relevant dimensions via regularities in the linguistic and physical environment. Thus, over development, children learn to attend to specific dimensions when making nominal category judgments--they selectively attend to shape, for example, when learning names for solid objects. In four experiments, I asked a question fundamental to our understanding of dimensional attention: does word learning scaffold attention to dimensional similarity in more general contexts. The results of Experiment 1 showed that children who are holistic classifiers are slower than dimensional classifiers to learn categories of objects that vary along both a category-relevant dimension (e.g. size) and a category-irrelevant dimension (e.g. brightness). However, the results of Experiment 2 showed that when children were presented with incidental labels during category learning, holistic classifiers learn the categories as quickly as dimensional classifiers. In a follow-up similarity classification task, children who had been holistic classifiers showed an increase in dimensional attention only if they had been in the label experiment. In Experiments 3 and 4, I examined category learning with and without a label in children who preferred to selectively attend to one dimension of similarity (e.g. brightness) regardless of whether this means selecting dimensional or holistic matches in a classification task. The results of these experiments provide a more complete picture of the continuous developmental trajectory of increasing selective and flexible dimensional attention. By showing how labels support dimensional attention, these results clarify the processes involved in development of similarity perception and potentially unify our understanding of attentional processes in word learning with those in a broader context.