Table 1. The abstract structure of the Shepard, Hovland, and Jenkins (1961) classification problems.

	Classification Category
Stimulus	I	II	III	IV	V	VI
1 1 1	A	A	B	B	B	B
1 1 2	A	A	B	B	B	A
1 2 1	A	B	B	B	B	A
1 2 2	A	B	A	A	A	B
2 1 1	B	B	A	B	A	A
2 1 2	B	B	B	A	A	B
2 2 1	B	A	A	A	A	B
2 2 2	B	A	A	A	B	A

Each stimulus can be coded as a binary vector along the three stimulus dimensions. The problems differ in how the eight items are assigned to the two categories. The perceptual dimensions (e.g., blue, stripe, border color) were randomly assigned to the abstract stimulus dimensions for each subject.