Table 1.

Abstract category structure

Category	Structure
Hole A beetles	2 2 2 2a
	1 1 1 2
	1 1 2 1
	1 2 1 1
Hole B beetles	1 2 2 2a
	2 1 1 2
	2 1 2 1
	2 2 1 1
Recognition test foils	1 1 1 1
	1 1 2 2
	1 2 1 2
	1 2 2 1
	2 2 2 2
	2 2 1 1
	2 1 2 1
	2 1 1 2

Each row represents a unique stimulus (i.e., beetle). The four values assigned to a stimulus denote the four stimulus dimensions (e.g., legs, antennae) assigned to a beetle. Each numeric value (1 or 2) represents a specific feature instantiation (e.g., red or green eyes). The first dimension represents the rule-relevant dimension. Most Hole A beetles have a 1 on the first dimension (e.g., thick legs), whereas most Hole B beetles have a 2 (e.g., thin legs). The first stimulus in each of the columns is therefore an exception. The recognition test foils were never presented in the categorization task and were saved for the surprise 2AFC recognition memory task. In each block of the 2AFC recognition task, each Hole A and Hole B beetle was paired with each of the recognition test foils with the same value on the rule dimension one time. For each subject, which physical dimension (eyes, tail, antennae, fangs, and legs) corresponded to the abstract feature dimensions (1s and 2s) was randomized, and the fifth physical dimension was held fixed.

^aException item.