Methylphenidate and stimulus control of avoidance behavior.
Methylphenidate can make avoidance responses faster yet still increase shocks, showing speed alone is not success.
01Research in Context
What this study did
Four rats lived in lever boxes around the clock. A tone sounded every 25 seconds. If the rat pressed the lever before the tone ended, it avoided a shock. If it pressed after the tone, it escaped the shock. The researchers gave each rat methylphenidate on some days and a salt-water shot on others. They counted how fast the rats pressed after the tone and how many shocks they still got.
What they found
On drug days the rats pressed faster right after the tone, so total lever presses went up. But three rats also got more shocks, not fewer. One rat almost stopped pressing late in the session and took many shocks. The drug sharpened the signal control for some rats and broke it for another.
How this fits with other research
Webb et al. (1999) moved the same drug into real classrooms. They showed that a brief time-out could calm kids with ADHD even when methylphenidate was already on board. The rat lab saw more shocks with the drug; the classroom study saw fewer disruptions with good contingencies. The difference is the setting, not the pill.
Goldman et al. (1979) gave pigeons cocaine or d-amphetamine and watched them mess up a color-matching task. Like the 1967 rats, the birds pressed faster at first but made more errors when the task demanded tight stimulus control. Both papers warn that stimulants can speed responding while weakening accuracy.
Mosk et al. (1984) kept the same avoidance box but raised shock intensity instead of using drugs. They also found a mixed picture: stronger shocks did not always help and sometimes disrupted timing. Together these studies show that both chemical and physical changes to the aversive event can backfire if the stimulus control is fragile.
Why it matters
If you use methylphenidate with clients, watch what the drug speeds up and what it breaks. Faster hands or words do not guarantee better learning or fewer aversive events. Pair the medicine with solid contingencies—clear signals, immediate reinforcement, and error correction—to keep the benefits and cut the shocks. Measure both rate and accuracy every session so you catch any drug-induced drift before it harms progress.
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02At a glance
03Original abstract
The introduction of a warning signal that preceded a scheduled shock modified the temporal distribution of free-operant avoidance responses. With response-shock and shock-shock intervals held constant, response rates increased only slightly when the response-signal interval was reduced. The result is consistent with Sidman's (1955) findings under different conditions, but at variance with Ulrich, Holz, and Azrin's (1964) findings under similar conditions. Methylphenidate in graded doses increased response rates, modifying frequency distributions of interresponse times. Drug treatment may have disrupted a "temporal discrimination" formed within the signal-shock interval. More simply, methylphenidate influenced response rates by increasing short response latencies after signal onset; this effect was more prominent than the drug's tendency to increase the frequency of pre-signal responses. When signal-onset preceded shock by 2 sec, individual differences in performance were marked; methylphenidate suppressed responding in one rat as a function of increasing dose levels to a greater degree than in a second animal, but both subjects received more shocks than under control conditions.
Journal of the experimental analysis of behavior, 1967 · doi:10.1901/jeab.1967.10-485