Stimulus selection and the number of stimulus components.

The number of word components in the compound stimuli of paired-associate lists were varied, and the words within a compound were presented either in a constant or in a variable order from trial to trial. The number of components, above one, had no appreciable effect on the difficulty of learning, and the variable order lists were more difficult than the constant order. Recall with the word components as cues showed that the amount of selection decreased with the variable order lists as the number of components increased. With the constant order lists, selection tended to remain constant as number of components increased. This was interpreted as the result of the availability of a rule for selection in the constant order conditions.