Doughty, A. H., & Richards, J. B. (2002).
Effects of reinforcer magnitude on responding under differential-reinforcement-of-low-rate schedules of rats and pigeons.
Journal of the Experimental Analysis of Behavior,
78, 17-30.
Experiment 1 investigated the effects of reinforcer magnitude on
differential-reinforcement-of-low- rate (DRL) schedule
performance in three phases. In Phase 1, two groups of rats
(n = 6 and 5) responded under a DRL 72-s schedule with
reinforcer magnitudes of either 30 or 300 µl of water. After
acquisition, the water amounts were reversed for each rat. In
Phase 2, the effects of the same reinforcer magnitudes on DRL
18-s schedule performance were examined across conditions. In
Phase 3, each rat responded under a DRL 18-s schedule in which
the water amounts alternated between 30 and 300 µl daily.
Throughout each phase of Experiment 1, the larger reinforcer
magnitude resulted in higher response rates and lower
reinforcement rates. The peak of the interresponse-time
distributions was at a lower value under the larger reinforcer
magnitude. In Experiment 2, 3 pigeons responded under a DRL 20-s
schedule in which reinforcer magnitude (1-s or 6-s access to
grain) varied from session to session. Higher response rates and
lower reinforcement rates occurred under the longer hopper
duration. These results demonstrate that larger reinforcer
magnitudes engender less efficient DRL schedule performance in
both rats and pigeons, and when reinforcer magnitude was held
constant between sessions or was varied daily. The present
results are consistent with previous research demonstrating a
decrease in efficiency as a function of increased reinforcer
magnitude under procedures that require a period of time without
a specified response. These findings also support the claim that
DRL schedule performance is not governed solely by a timing
process.
Key words: differential-reinforcement-of-low-rate schedule,
interresponse time, reinforcer magnitude, bar press, key peck,
rat, pigeon