The role of selective attention in preschoolers' rule use in a novel dimensional card sort

Preschoolers often fail in switching between dimensions in sorting cards. To evaluate proposed cognitive constraints, we introduced a "same-silly" task, not requiring an extra-dimensional shift. Instructions were to sort cards so that the shapes were the same ("same" game) or not the same ("silly" game) as targets. In Experiment 1, using b/w line drawings, 3-year-olds successfully played both "same" and "silly" games. In Experiments 2 and 3, with the irrelevant dimension of color added to cards, most children below 4;6 perseverated on the "same" game, revealing an effect of stimulus complexity on rule-based reasoning. Thus, with uni-dimensional stimuli, 3-year-olds flexibly alternated between "same" and "silly" rules, but could not follow identical rules with bi-dimensional stimuli requiring selective attention to shape. We suggest that preschoolers' difficulties in selective attention, rather than the presence of an extra-dimensional shift, lead to card sorting failure. (C) 2003 Elsevier Science Inc. All rights reserved.