Sumpter, C. E., Temple, W., & Foster, T. M. (1998).
Response form, force, and number: Effects on concurrent-schedule performance.
Journal of the Experimental Analysis of Behavior,
70, 45-68.
Six hens responded on concurrent variable-interval (key-peck)
variable-interval (door-push) schedules of reinforcement in which
the second-order (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 manipulations of
fixed-ratio requirement and required response force differed in
their effects. The manipulations of fixed-ratio size affected the
response and time measures differently, producing fairly
constant, multiplicative biases only in terms of response
allocation. It was argued that variations in fixed-ratio size
necessarily change the time allocated to that response unit, and
thus changes in time bias were not necessarily a fundamental
effect of changing the ratio. In contrast, the changes in
response bias were a fundamental result of changes in ratio size.
The response-force manipulations produced similar bias shifts in
terms of response and time allocation, but they appeared to
combine with relative reinforcement rate to affect choice
interactively. Specifically, behavior appeared to be biased
towards the least effortful (i.e., key-peck) response, but the
increases in door force had a larger effect on bias when the hens
were making this response infrequently (on a lean schedule). The
different effects of the fixed-ratio and response-force
manipulations on concurrent performance were partially accounted
for by the differing times required to complete each response
unit under those manipulations, but this would not account for
the interaction. The interaction would be consonant with
increased response effort decreasing the effective value of the
associated reinforcement schedule.
Key words: concurrent schedules, second-order schedules, response
form, response force, key peck, door push, hens