Figure 1.

Stimuli for the object discrimination and size judgment tasks. Participants viewed pairs of squares or blob-like objects (comprised of three features – outer shape, inner shape, and fill pattern) and indicated whether or not the simultaneously presented stimuli were a match or a nonmatch. In the match conditions, both objects and squares were identical to one another. There were two nonmatch conditions for each stimulus type: Difficult and Easy. The Difficult Object pairs differed by one of the three features (in this figure, the inner shape differs). Easy Object pairs differed on all three features. For the Difficult and Easy Size judgments, squares differed from one another by 2–4mm and 5–8mm, respectively.