The role of elicited responding in behavioral contrast.

An attempt was made to separate operant and elicited pecks occurring in multiple schedules of food reinforcement by moving the component stimuli to a second key, upon which pecks had no effect. The operant key stimulus was constant, regardless of the reinforcement schedule in effect. Experiments included two- and three-component multiple schedules and a comparison of the single-key and the two-key procedures. In general, conditions that typically produce positive contrast in single-key procedures reduced responding to the constant-stimulus key (induction) and increased responding to the component-stimulus key (contrast) in the two-key procedure. The results were interpreted as supporting the contention that two response classes, operant and elicited, are present in standard multiple schedules. In addition, elicited responses were strongly implicated in contrast phenomena.