Effect of drugs on response-duration differentiation VII: response-force requirements.
Lower the force requirement if you want clean duration control; stimulants and high effort both erode timing.
01Research in Context
What this study did
McClure et al. (2000) asked pigeons to peck a key for food. The birds had to hold each peck for a set time. If the peck was too short, no food.
The team then changed how hard the birds had to press. They also gave the birds two drugs: PCP and methamphetamine. They watched how these changes hurt or helped timing.
What they found
Heavy force made the birds rush. Most pecks ended too soon, so accuracy dropped. Light force helped the birds hit the target time.
Both drugs made timing worse in a dose-by-dose way. When force was high, the drugs made the damage even bigger.
How this fits with other research
McIntyre et al. (2002) also saw amphetamine hurt timing, but they said the drug works by changing response rate, not the “inner clock.” McClure et al. (2000) match this view: meth made more short, fast pecks.
Harris et al. (1978) showed that an animal’s past rate sets whether amphetamine will speed or slow it. The 2000 birds with high-force history acted like the high-rate rats: both got worse under stimulant.
Duker et al. (1991) added force and duration sensors too. They proved that different drugs change force in different ways. McClure et al. (2000) extend that idea: force level itself can amplify or buffer drug damage.
Why it matters
When you shape a duration-based skill—holding a spoon, waiting at the curb, sustaining a vowel—keep the force demand low at first. Light effort lets the learner feel the exact time. Save heavy pressure for later, and skip session days if the client takes stimulant meds or shows motor side effects. Check timing accuracy early and often; it is the first thing drugs and fatigue will steal.
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02At a glance
03Original abstract
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.
Journal of the experimental analysis of behavior, 2000 · doi:10.1901/jeab.2000.74-295