Macenski, M. J., & Meisch, R. A. (1998).
Ratio size and cocaine concentration effects on oral cocaine-reinforced behavior.
Journal of the Experimental Analysis of Behavior,
70, 185-201.
Monkeys were given a choice between cocaine solutions and water
under concurrent fixed-ratio reinforcement schedules. The operant
response was spout contact. Six rhesus monkeys served as
subjects. The cocaine concentration was varied from 0.0125 to 0.8
mg/ml, and the fixed-ratio value was varied from 8 to 128.
Cocaine maintained higher response rates than did water over a
wide range of conditions. Response rate and number of cocaine
deliveries per session were inverted U-shaped functions of
concentration. These functions were shifted to the right as the
fixed ratio was increased. The number of cocaine deliveries was
more persistent as fixed-ratio value was increased when the unit
dose was larger rather than smaller. Cocaine consumption was
analyzed as a function of unit price (fixed-ratio value divided
by cocaine concentration), and unit price accounted for between
77% and 92% of the variance in cocaine consumption for individual
monkeys. The current data support the claim that a drug's
reinforcing effects increase directly with dose and underscore
the need to gather parametric data when examining the effects of
experimental manipulations on a drug-reinforced baseline.
Key words: oral cocaine self-administration, relative reinforcing
effects, behavioral momentum, behavioral economics, fixed-ratio
schedules, spout contact, rhesus monkeys