Figure 1.

Examples of rule-based and information-integration category structures. The stimuli are sine-wave disks varying in bar width and orientation. In the top panel, the vertical decision bound shows that only variation in bar width carried diagnostic category information, so optimal performance was governed by a one-dimensional (bar-width) rule. In the lower panel, the diagonal decision bound shows that bar width and orientation both carry category information—information from both dimensions must be integrated into a category decision. Each panel illustrates some of the three hundred stimuli that were selected from within the exemplar space of Category A and Category B using methods described in the text.