The effects of morphine on fixed-interval patterning and temporal discrimination.
Morphine flattens fixed-interval scalloping and hurts temporal discrimination accuracy, but not by simply making pigeons think time is passing faster.
01Research in Context
What this study did
Heavey et al. (2000) gave pigeons repeated fixed-interval schedules.
Birds pecked for food every few minutes.
Then the team injected morphine to see how the drug changed timing and response pattern.
What they found
Morphine flattened the normal scallop shape.
Birds also made more timing errors on both short and long intervals.
The drug hurt accuracy, but it did not simply make the birds feel time was rushing by.
How this fits with other research
Fantino (1967) and Dews (1966) showed that, without drugs, pigeons pause after food and then speed up, creating a clear curve.
Heavey et al. (2000) now shows that morphine wipes out that curve, proving the timing system can be knocked offline.
Green et al. (1987) taught birds to tell short from long flashes; extra cues helped them learn faster.
The new study finds that, even when the interval cues stay the same, morphine still wrecks accuracy, so the fault is inside the clock, not in the signal.
Why it matters
If a client’s medication makes timing sloppy, you may see uneven pauses, early responses, or missed waits.
Check for flat scallops or drifting DRL performance.
When this happens, add extra visual timers or shorten the interval until the behavior firms up again.
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02At a glance
03Original abstract
Changes produced by drugs in response patterns under fixed-interval schedules of reinforcement have been interpreted to result from changes in temporal discrimination. To examine this possibility, this experiment determined the effects of morphine on the response patterning of 4 pigeons during a fixed-interval 1-min schedule of food delivery with interpolated temporal discrimination trials. Twenty of the 50 total intervals were interrupted by choice trials. Pecks to one key color produced food if the interval was interrupted after a short time (after 2 or 4.64 s). Pecks to another key color produced food if the interval was interrupted after a long time (after 24.99 or 58 s). Morphine (1.0 to 10.0 mg/kg) decreased the index of curvature (a measure of response patterning) during fixed intervals and accuracy during temporal discrimination trials. Accuracy was equally disrupted following short and long sample durations. Although morphine disrupted temporal discrimination in the context of a fixed-interval schedule, these effects are inconsistent with interpretations of the disruption of response patterning as a selective overestimation of elapsed time. The effects of morphine may be related to the effects of more conventional external stimuli on response patterning.
Journal of the experimental analysis of behavior, 2000 · doi:10.1901/jeab.2000.74-229