RESPONSE FORM, FORCE, AND NUMBER - EFFECTS ON CONCURRENT-SCHEDULE PERFORMANCE

Six hens responded on concurrent variable-interval (key-peck) variable -interval (door-push) schedules of reinforcement in which the second-o rder (fixed-ratio) requirements on the alternatives (Experiment 1) or the required door forces (Experiment 2) were varied. The key-peck and door-push response (measured as fixed-ratio completion) and time data were well described by the generalized matching law. However, the mani pulations of fixed-ratio requirement and required response force diffe red in their effects. The manipulations of fixed-ratio size affected t he response and time measures differently, producing fairly constant, multiplicative biases only in terms of response allocation. It was arg ued that variations in fixed-ratio size necessarily change the One all ocated to that response unit, and thus changes in time bias were not n ecessarily a fundamental effect of changing the ratio. In contrast, th e changes in response bias were a fundamental result of changes in rat io size. The response-force manipulations produced similar bias shifts in terms of response and time allocation, but they appeared to combin e with relative reinforcement rate to affect choice interactively. Spe cifically, behavior appeared to be biased towards the least effortful (i.e., key-peck) response, but the increases in door force had a large r effect on bias when the hens were making this response infrequently (on a lean schedule). The different effects of the fixed-ratio and res ponse-force manipulations on concurrent performance were partially acc ounted for by the differing times required to complete each response u nit under those manipulations, but this would not account for the inte raction. The interaction would be consonant with increased response ef fort decreasing the effective value of the associated reinforcement sc hedule.