Miller, M. L., Wade Brodkorb, G., & Branch, M. N. (2001).
Tolerance to the effects of cocaine on performance under behavior-correlated reinforcement magnitude.
Journal of the Experimental Analysis of Behavior,
76, 217-234.
Four pigeons responded under a fixed-interval 8-min schedule of
food delivery in which the amount of food delivered at the end of
each interval depended on performance during the interval (i.e.,
a correlated schedule). Specifically, duration of access to grain
was contingent upon the number of responses made during the first
4 min of the interval. This differential outcome did not affect
response rates or patterning relative to performance under a
simple fixed-interval 8-min schedule. Behavior under the
correlated schedule was then investigated under doses of cocaine
ranging from 0.3 to 10.0 mg/kg. A bitonic dose– response
function was obtained for response rates and the time with head
in the food hopper, whereas dose-dependent decreases were
observed in the mathematical index of curvature (Fry, Kelleher,
& Cook, 1960). The dose that produced the greatest increase
in the head-in-hopper time was then administered prior to each
session. Following repeated administration of cocaine,
disruptions in response patterning were attenuated for all 4
pigeons; tolerance was also observed to the rate-increasing
effects and increased head-in-hopper time for 2 pigeons after
chronic cocaine administration. Tolerance therefore developed
despite the fact that the initial effect of cocaine was to
increase the amount of food obtained.
Key words: fixed-interval schedule, cocaine, tolerance,
reinforcement loss, correlated schedule, key peck, pigeons