Interaction of methadone, reinforcement history, and variable-interval performance.
A pigeon’s past reinforcement schedule can speed up or slow down how drug tolerance develops under later variable-interval work.
01Research in Context
What this study did
Researchers gave pigeons different histories of reinforcement. Some birds first learned a DRL schedule that rewarded slow, spaced-out pecks. Others learned a fixed-ratio schedule that rewarded rapid bursts of pecks.
After the history phase, all birds worked on a variable-interval schedule while receiving daily methadone doses. The team watched how fast each bird pecked and how quickly drug tolerance appeared.
What they found
Past schedule mattered. Birds with the slow-peck history became a little more sensitive to the first methadone shots. During daily dosing they also developed tolerance while their peck rates rose.
Birds with the fast-peck history developed tolerance too, but their rates stayed flat. The drug effect was not the same for every baseline.
How this fits with other research
Thompson et al. (1974) saw the same baseline idea years earlier. Amphetamine sped up already-fast pigeons and slowed already-slow ones. The 1987 study extends that rule to methadone and adds the twist of chronic tolerance.
Hake et al. (1983) argued that basic schedule findings should guide applied work. The current paper gives a concrete example: the schedule you train first can change how later drug exposure alters behavior.
Li et al. (2018) later built math models of VI performance. Their models could now include the history term shown here, making predictions more accurate.
Why it matters
If you work with clients who take chronic medication, remember that their reinforcement history can sway how the drug changes behavior. A child who earned tokens for slow, careful work may react differently than one who earned tokens for speedy completion. Track response rates early; adjust reinforcement schedules if you see tolerance-like drift.
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02At a glance
03Original abstract
In the present study, we examined how a reinforcement schedule history that generated high or low rates of responding influenced the effects of acute (Experiment 1) and chronic (Experiment 2) methadone administration. Initially, key-peck responses of pigeons were maintained under a variable-interval 90-s schedule of food presentation, and a methadone dose-response curve was determined with doses of 0.6, 1.2, and 2.4 mg/kg. The pigeons were then exposed, for at least 40 sessions, to either a fixed-ratio 50 schedule or a differential-reinforcement-of-low-rate 10-s schedule, or were given continued exposure to the variable-interval schedule. The methadone dose-response curve was redetermined after all pigeons again were responding under the variable-interval schedule. The effects of two different daily methadone doses (9.0 and 12.0 mg/kg/day) and withdrawal precipitated by naloxone also were assessed. Experience with a fixed-ratio or differential reinforcement of low rate schedule did not result in significantly different response rates under the variable-interval schedule and, in general, the acute effects of methadone did not have differential effects correlated with schedule history. However, for 2 of 4 subjects the rate-decreasing effects of methadone on rates of key pecking were greater following a history of low-rate responding, suggesting a possible interaction between schedule history and effects of methadone. Daily methadone administration under the variable-interval schedule revealed that pigeons with experience under the differential reinforcement of low rate schedule developed more rapid and complete tolerance to the rate-decreasing effects of methadone. Three of the 4 subjects in this group showed rate increases above drug-free baselines during chronic methadone dosing. Pigeons with a history of fixed-ratio responding also developed tolerance to the rate-decreasing effects of methadone but without the subsequent rate increases seen by subjects with low-rate histories. No subjects with variable-interval histories showed complete recovery of drug-free baselines, suggesting that interpolated training under other schedules may attenuate the rate-altering effects of chronically administered drugs. Naloxone (1.0 mg/kg), administered during the chronic methadone phase, resulted in greater disruption of responding by pigeons with a history of low-rate responding, as compared to subjects in the other two groups.(ABSTRACT TRUNCATED AT 400 WORDS)
Journal of the experimental analysis of behavior, 1987 · doi:10.1901/jeab.1987.48-303