A sequential response method of studing complex behavior in animals and its application to the measurement of drug effects.
Complex response chains fall apart first under drugs, so track the hardest chain as a quick toxicity probe.
01Research in Context
What this study did
FARMELong (1963) taught rats to press levers in a set order: left, right, middle.
Each rat had to finish the three-press chain to earn food.
After the sequence was rock-solid, the rats got shots of a hallucinogenic drug.
The scientist then counted how many chains the rats still finished correctly.
What they found
Small drug doses wrecked the long chain first.
Rats still pressed, but they lost the order.
The harder the sequence, the less drug it took to break it.
A simple left-right pattern stayed intact at doses that ruined the three-step version.
How this fits with other research
Garcia et al. (1973) saw the same crash when a scary shock cue was added.
Their rats also forgot the long chain, showing drugs and fear hit complex behavior alike.
Goldman et al. (1979) gave pigeons cocaine and d-amphetamine.
They found learning tasks broke at lower doses than rote performance, matching the dose-complexity link J spotted.
Podlesnik et al. (2023) sweep 200 basic rat studies and show this drug-plus-chain design is still a gold standard for spotting relapse risk.
Why it matters
When you test a client’s skill, start simple and watch the chain length.
If a new medicine, sleep loss, or stressor arrives, recheck the longest chain first—it will fail earliest.
Use this as an early warning instead of waiting for the whole skill to collapse.
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02At a glance
03Original abstract
A behavioral testing method was demonstrated to be applicable to the study of detrimental drug effects on complex behavior in rats. The method required the subject (S) to respond in a certain sequence to four identical response sites spaced 90 degrees apart within a cylindrical test compartment. After each S was shaped to perform its one particular sequence within this quadrilaterally symmetrical environment, and its performance was brought to a stable level, drug effects were then studied on a battery of such Ss whose sequential response habits were representative of a continuum of sequence complexity. Experiments with a drug which induces hallucinatory and confusional states in man showed that the method yields in the rat quantitative measures of detrimental behavioral effects in terms of dose-response and dose-time relationships in addition to providing an estimate of the interactive effect between drug dose and behavioral complexity. It was found that for a given magnitude of behavioral detriment, drug dose and behavioral complexity of sequence were inversely related. That is, a S required to perform a simple sequence needed a larger drug dose to interfere with its habit a unit amount that did a S with a more complex one; or, expressed another way, a given drug dose had a greater behavioral effect the more complex the sequence. Finally, an empirical ranking of response sequences along a functional behavioral complexity dimension was presented.
Journal of the experimental analysis of behavior, 1963 · doi:10.1901/jeab.1963.6-271