McClure, G. Y. H., Hardwick, W. C., & McMillan, D. E. (2000).
Effect of drugs on response-duration differentiation vii: Response-force requirements.
Journal of the Experimental Analysis of Behavior,
74, 295-309.
Rats were trained to press a lever for at least 1 s but for less
than 1.3 s. The force required to press the lever was then
increased or decreased by 10, 15, or 20 g. Increases in the force
requirements for lever pressing decreased timing accuracy, but
decreases in the force requirement had the opposite effect.
Accuracy decreases at increasing force requirements were
characterized by an increase in the relative frequency of
responses that were too short to meet the reinforcement
criterion. In contrast, increases in accuracy when the force
requirements were decreased were characterized by increases in
response durations that met the reinforcement criterion and
decreases in the relative frequency of responses that were too
short to produce the reinforcer. Phencyclidine (PCP) and
methamphetamine produced dose-dependent decreases in accuracy
that were associated primarily with increases in the relative
frequency of short response durations, although methamphetamine
also produced increases in long response durations at some doses.
When the effects of PCP were determined with the force
requirement increased by 10 g or decreased by 15 g, the
cumulative response-duration distribution shifted toward even
shorter response durations. When the effects of methamphetamine
were determined with the force requirement on the lever increased
by 10 g, the cumulative frequency distribution was shifted toward
shorter response durations to about the same extent as it had
been before force requirements increased; however, when the force
required to press the lever was decreased by 15 g, these shifts
toward shorter response durations almost completely disappeared.
These results show that increases and decreases in the force
requirements for lever pressing have different effects on the
accuracy of temporal response differentiation.
Key words: temporal response differentiation, methamphetamine,
phencyclidine, response force, lever press, rat