The effects of morphine on the production and discrimination of interresponse times.
Morphine blurs pigeons' sense of their own response timing without making time feel longer.
01Research in Context
What this study did
Matson et al. (2004) gave pigeons morphine and watched how well they could sort their own response times.
Birds pecked a key and learned to call each gap between pecks either short or long.
The team then compared choices after saline shots to choices after morphine shots.
What they found
Morphine flattened the usual hump in the response-time curve.
The birds still pecked, but they were worse at labeling the long gaps correctly.
Time did not feel longer to them; they just got sloppy at telling it apart.
How this fits with other research
McAuley et al. (1986) saw a similar timing mess in rats given d-amphetamine. Both drugs scramble temporal cues, even though the animals and chemicals differ.
Davison et al. (1991) used the same morphine dose in pigeons and found a different pattern: avoidance stayed strong while timeout responding dropped. The drug hurts some performances but leaves others alone, so timing tasks are simply more fragile.
Hart et al. (1968) showed that, without any drug, pigeons already scatter their response times under VI schedules. Matson et al. (2004) reveal that morphine makes this natural scatter even worse, proving the baseline was never tight to begin with.
Why it matters
If you run precision-teaching fluency checks or differential-reinforcement-of-low-rate programs, remember that outside factors can flatten a learner's sense of time. Watch for drift after medication changes. Build in extra prompts or shorter timing windows when temporal discrimination must stay sharp.
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02At a glance
03Original abstract
Recent experiments suggest that the effects of drugs of abuse on the discrimination of the passage of time may differ for experimenter-imposed and subject-produced events. The current experiment examined this suggestion by determining the effects of morphine on the discrimination of interresponse times (IRTs). Pigeons pecked a center key on a random-interval 20-s schedule of matching-to-sample trials. Once the interval had timed out, a choice trial randomly followed either a short (2- to 3-s) or long (6- to 9-s) IRT on the center key. Pecking the side key lit one color produced food after a short IRT, and pecking the side key lit the other color produced food after a long IRT. Two experimental phases differed in the functional role of the different key colors. Under control conditions, the IRT distributions had two modes, one at the lower bound of the short category and a smaller one at the lower bound of the long category. Pigeons accurately categorized the duration of the IRTs: One key color was pecked following short IRTs and the other key color was pecked following long IRTs. Morphine flattened the IRT distribution and reduced the accuracy of categorizing IRTs. Categorization of long IRTs was particularly disrupted. Morphine did not produce overestimation of time as assessed by the production or categorization of IRTs. These results are similar to those obtained previously for the effects of morphine on the discrimination of the duration of experimenter-imposed events.
Journal of the experimental analysis of behavior, 2004 · doi:10.1901/jeab.2004.82-197