Stimulus selection in paired-associate learning is assumed to be the result of an active organized process. From this standpoint, a methodological analysis and review of the studies of stimulus selection are presented. Some suggestions are made for further studies of stimulus selection. Underwood (1963) called attention to the fact that subjects often select part of the nominal stimulus as the functional stimulus. He discussed some of the implications of stimulus selection and suggested that selection occurs in rote paired-associate learning as well as in concept formation. Shepard (1963), in his comments on Underwood's paper, maintained that some stimuli (e.g., nonsense trigrams and geometrical figures) are almost inevitably analyzed into components or dimensions, while others (e.g., colors and olfactory stimuli) are almost invariably reacted to as unitary, unanalyzable wholes. He distinguished between selective attention or abstraction which applies to the former type of stimuli and pure stimulus generalization which applies to the latter. Shepard also suggested that functional stimuli, in some cases, are not merely constructed from the individual nominal stimuli but, in addition, are organized into an array or "cognitive map."These discussions emphasized the fact that, even during paired-associate learning, human subjects are not passive receivers of stimuli, but are active selectors and organizers. When presented with a complex stimulus, subjects abstract part of it for use as the functional 1 The author is grateful to Benton J. Underwood for his comments on an earlier draft.2 Request for reprints should be sent to Jack