Effects of methadone on alternative fixed-ratio fixed-interval performance: latent influences on schedule-controlled responding.
Methadone can swing control from ratio to interval schedules, so medication changes can masquerade as treatment failure.
01Research in Context
What this study did
Scientists gave pigeons a two-part key-peck schedule. Peck 30 times and food drops. Wait 5 minutes and the first peck brings food. The two parts switch back and forth within each session.
After birds settled into the pattern, the team injected different doses of methadone. They watched which part of the schedule now controlled most of the birds’ pecks.
What they found
Low methadone doses made the birds pay more attention to the 5-minute wait. They slowed their 30-peck runs and saved most responses for the interval half.
Higher doses almost wiped out the ratio burst. The birds acted as if the fixed-ratio rule had vanished and only the fixed-interval rule mattered.
How this fits with other research
Hearst (1960) first showed that amphetamine fires up fixed-ratio responding in pigeons. Davison et al. (1989) flips the picture: methadone quiets that same ratio performance. Same species, same chamber, opposite drug effect.
Capriotti et al. (2017) tested fixed versus progressive DRO schedules with kids. Both papers ask, "Which schedule grabs behavior when options compete?" One uses drugs to reveal the answer; the other tweaks the rule itself.
Exline et al. (2024) taught parents to run multiple schedules over telehealth. Their natural-cue transfer echoes the pigeons’ shift in rule following, showing schedule control can jump across settings and species.
Why it matters
If a client’s behavior suddenly flips from one schedule to another, check for new meds before you rewrite the plan. Methadone, and maybe other opioids, can make kids or adults ‘listen’ only to the interval part of a mixed schedule. You may need to shorten the interval or add prompts until the drug effect fades.
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Join Free →Graph each component of your mixed schedule separately; if interval responding jumps after a med change, adjust the timing before you blame the intervention.
02At a glance
03Original abstract
Effects of methadone on pigeons' key pecking were examined under four conditions selected to analyze the control of behavior under alternative fixed-ratio fixed-interval schedules. In Condition 1, pigeons pecked under one of three different alternative schedules (alternative fixed-ratio 50 fixed-interval 90 s, alternative fixed-ratio 75 fixed-interval 90 s and alternative fixed-ratio 200 fixed-interval 90 s) each week. In Condition 2, fixed-ratio 50 or fixed-ratio 75 schedules were in effect during baseline sessions, and alternative fixed-ratio 50 fixed-interval 90-s or alternative fixed-ratio 75 fixed-interval 90-s schedules were in effect during sessions in which methadone was administered. In Condition 3, effects of methadone on key pecking maintained under fixed-ratio 50 and fixed-ratio 75 schedules were examined, whereas in Condition 4 the effects of methadone on key pecking under a fixed-interval 90-s schedule as well as fixed-ratio 50 and fixed-ratio 75 schedules were investigated. Control by the fixed-interval contingency was assessed by computing the proportion of total session reinforcers delivered under the fixed-interval schedule. Methadone administration (0.5-4.0 mg/kg) shifted the predominant source of schedule control under the alternative schedule from the fixed-ratio schedule to the fixed-interval contingency. This shift was dependent on methadone dose and fixed-ratio size. Control by the fixed-interval contingency was greatest following extensive exposure to the interval component embedded within the alternative schedule (Condition 1), but was apparent to a lesser degree with even very limited exposure to the alternative fixed-ratio fixed-interval schedule (Condition 2). Interreinforcement intervals comparable to those under fixed-interval schedule were not observed under the fixed-ratio schedules presented alone (Condition 3). Repeated exposure to the fixed-interval contingency outside the context of the alternative fixed-ratio fixed-interval schedule did not engender performance changes under a fixed-ratio schedule which would mimic those of increased fixed-interval contingency control (Condition 4). These data suggest that drug administration can be used to unmask the influence of contingencies that are latent under baseline conditions and reveal influences of both past and present environmental variables.
Journal of the experimental analysis of behavior, 1989 · doi:10.1901/jeab.1989.52-141