Walker, D. J., & Branch, M. N. (1996).
Effects of cocaine on briefly signaled versus completely signaled delays to reinforcement.
Journal of the Experimental Analysis of Behavior,
65, 375-388.
Key pecking by 4 pigeons was maintained by a multiple schedule
consisting of two variable-interval 60-s schedules wherein each
food presentation followed a nonresetting 27-s delay that was
either briefly signaled at its outset or completely signaled.
Brief-signal duration was adjusted so that response rates
maintained by the briefly and completely signaled delays of
reinforcement were similar. In general, acute administration of
small to intermediate doses (0.3 to 3.0 mg/kg) of cocaine
produced either small increases in response rates in both
components or no change, and larger doses (5.6 to 13.0 mg/kg)
decreased response rates. Chronic (i.e., daily) cocaine
administration (10.0 mg/kg) resulted in tolerance to the
rate-decreasing effects in both components. Cocaine's effects
were generally similar whether delays were completely or briefly
signaled. Discontinuation of cocaine administration and
subsequent removal of the delay signals also had similar effects
in both components of the multiple schedule. Taken together,
these results are consistent with the view that the two types of
delay signals were equally effective in maintaining responding
during the variable-interval schedules.
Key words: signaled delay of reinforcement, conditioned
reinforcement, cocaine, tolerance, variable-interval schedule,
key peck, pigeons