Stimulus compounding in free-operant and classical conditioning: A review and analysis.

Abstract

Free-operant and classical conditioning studies reporting additive summation, suppressive summation, and response averaging to compounded stimuli are reviewed, and a stimulus control model applicable to additive and suppressive summation in both paradigms is presented. A symmetrical composite-stimulus continuum, denned by the on-off states of the discriminative or conditioned stimuli controlling behavior in training, is seen to be common to both types of summation, with the functions of the ail-on and ail-off continuum extremes interchangeable. Moreover, additive summation, suppressive summation, and response averaging appear to be dependent on discrimination training, and determined by the history of, as well as the immediate relations between, response outputs and reinforcement densities conditioned to particular stimulus values along the composite training dimension. This evidence, and the stimulus control model derived therefrom, are used to functionally relate summation to generalization peak shift and to suggest that these additive, suppressive, and averaging effects to compounded stimuli might further help in clarifying, and in placing in contextual perspective, what are currently thought of as excitatory and inhibitory mechanisms in learning. This review presents the current status of stimulus-compounding research in free-operant and classical conditioning,3 and through this presentation it attempts to develop a comprehensive functional analysis of the variables involved in determining the various behavioral resultants reported within this experimental paradigm. The scope of the present paper does not extend to multiple-resp onse or multiplechoice procedures, exemplified by the experiments of Schoeffler (1954) and Atkinson, Calfee, Sommer, Jeffrey, and Shoemaker (1964), but instead focuses on unitary response paradigms where variations in rates or magnitudes of response are of primary concern. Ultimately, the stimulus control analysis formulated is (a) discussed in terms of some