Interval and ratio reinforcement of a complex sequential operant in pigeons.
Once a response chain becomes a unit, the chain keeps its shape even when the reinforcement schedule changes.
01Research in Context
What this study did
The researcher taught pigeons a four-peck chain on one key. Each bird had to hit the key in the same order every time to earn food.
After the chain was rock-solid, the birds worked under two schedules. One was fixed-interval two minutes. The other was fixed-ratio four responses. The study watched what stayed the same and what changed.
What they found
The four-peck pattern locked in like a habit. It stayed the same whether the bird was on FI or FR. The timing inside the chain also stayed put.
Only the pause before the first peck moved with the schedule. FI made the pause longer. FR made it shorter. The chain itself refused to bend.
How this fits with other research
Quilitch et al. (1973) saw the opposite. They paid birds for varying their response order, yet the birds still got more rigid. That paper warns that simply reinforcing variety may not stop stereotypy. Schwartz (1982) shows that once a chain is fixed, the schedule alone cannot unlock it.
Hoffman et al. (1966) and Blackman (1970) laid the groundwork. They proved pigeons feel the difference between FR and FI schedules. Schwartz (1982) moves the question forward: the schedule still controls pause time, but not the shape of a locked-in chain.
Sachs et al. (1969) found that intermittent schedules increase location variability. Schwartz (1982) adds a twist: variability rises in some places (pause) while form stays frozen in others (sequence).
Why it matters
For clinicians, the message is clear. If a learner practices the same response chain every day, the pattern can turn into a unit that later schedules cannot easily break. You may change the pause, but the order can stick. Build flexibility early or plan extra steps to loosen the chain later.
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02At a glance
03Original abstract
Pigeons were required to produce exactly four pecks on each of two keys in any order for reinforcement. Correct response sequences were reinforced on either fixed-interval two-minute or fixed-ratio four schedules, with each correct sequence treated as a single response. Each pigeon developed a particular dominant sequence that accounted for more than 80% of all sequences. Sequence stereotypy was relatively unaffected by the temporal properties of the fixed-interval and fixed-ratio schedules. Response time (time from the first response in each sequence to the last) was also relatively unaffected by the temporal properties of the schedules. In contrast, response latency (time from end of one sequence to the beginning of the next) was markedly affected by the schedules. Latencies were long early in the interreinforcement interval and got shorter as the interreinforcement interval progressed. These data suggest that stereotyped response sequences become functional behavioral units, resistant to disruption or alteration by reinforcement variables that ordinarily influence the temporal spacing of individual responses.
Journal of the experimental analysis of behavior, 1982 · doi:10.1901/jeab.1982.37-349