Sequential patterns in post-reinforcement pauses on fixed-interval schedules of food.
Post-reinforcement pauses on long FI schedules alternate long-short, but you can wipe the pattern out with a brief work window.
01Research in Context
What this study did
Shull (1971) watched pigeons work on a five-minute fixed-interval schedule.
The birds pecked for food, then paused. The team tracked how long each pause lasted.
Later, they added a short work window right after food. This let them test if the pause pattern was forced by the schedule itself.
What they found
The pauses alternated: long, short, long, short, in a steady rhythm.
When the work window was added, the alternation vanished.
The pattern was not built into the bird; it was created by the schedule.
How this fits with other research
Fantino (1969) saw a similar see-saw effect across short and long FI cycles. The new study shows the swing can happen inside one steady schedule.
Harzem et al. (1978) later paid birds for long pauses and saw pauses shrink. Shull (1971) had already shown you can erase the pattern by tightening the work rule. Both prove pause length is flexible, not fixed.
Halpern et al. (1966) linked longer pauses to bigger ratio demands. The 1971 paper moves the lens to interval schedules and finds order in the pause sequence, not just its length.
Why it matters
Your client’s break after reinforcement is not noise—it is data. If you see long-short-long-short pauses, check the schedule, not the learner. Tighten the response window, add an early prompt, or change the interval and the alternation can flatten. Use this to build smoother work cycles in skill labs or during DRL routines.
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02At a glance
03Original abstract
Responding by one pigeon was reinforced with food on fixed-interval schedules of 30, 60, and 300 sec duration. A second pigeon was studied under fixed-interval durations of 60 and 300 sec. For both birds, the average post-reinforcement pause was one-half the duration of the fixed interval. Autocorrelation coefficients revealed first-order sequential dependencies in series of post-reinforcement pauses. On the 300-sec fixed-interval schedule, successive post-reinforcement tended to alternate between long and short durations. At the shorter fixed-interval durations there was less evidence of alternation sequences. A second experiment was conducted to determine if the time intervals between the first response after reinforcement and the next reinforcement (the work periods) were responsible for the alternation patterns in the series of post-reinforcement pauses. To evaluate the role of the work period, several procedures were used to modify the work period from that obtained on the fixed-interval 300-sec schedule. Adding a schedule to the fixed-interval schedule that set the minimum amount of time that could elapse between the first response after reinforcement and the next reinforcement eliminated the alternation pattern. Control schedules indicated that the elimination of alternation patterns resulted from constraints on the work period per se and not from confounded changes in the interreinforcement intervals.
Journal of the experimental analysis of behavior, 1971 · doi:10.1901/jeab.1971.15-221