Keely, J., Feola, T. & Lattal, K.A. (2007).
Contingency tracking during unsignaled delayed reinforcement.
Journal of the Experimental Analysis of Behavior, 88, 229-247.
Three experiments were conducted with rats in which responses on one lever (labeled the functional lever) produced
reinforcers after an unsignaled delay period that reset with each response during the delay. Responses on a
second, nonfunctional, lever did not initiate delays, but, in the first and third experiments, such responses
during the last 10 s of a delay did postpone food delivery another 10 s. In the first experiment, the location of
the two levers was reversed several times. Responding generally was higher on the functional lever, though the
magnitude of the difference diminished with successive reversals. In the second experiment, once a delay was
initiated by a response on the functional lever, in different conditions responses on the nonfunctional lever
either had no effect or postponed food delivery by 30 s. The latter contingency typically lowered response rates
on the nonfunctional lever. In the first two experiments, both the functional and nonfunctional levers were
identical except for their location; in the third experiment, initially, a vertically mounted, pole-push lever
defined the functional response and a horizontally mounted lever defined the nonfunctional response. When the
roles of the two responses were reversed, vertical-lever response rates were higher. These results taken together
suggest that responding generally tracked the response–reinforcer contingency. The results further show how
nonfunctional-operanda responses are controlled by a prior history of direct reinforcement of such responses, by
the temporal delay between such responses and food delivery, and as simple generalization between the two
operanda.
Key words: unsignaled delay of reinforcement, contingency tracking,
discrimination, lever press, pole-push response, rats