Timing in response-initiated fixed intervals.
Letting the learner start the fixed interval scrambles the usual timing pattern, so add an external cue when precision matters.
01Research in Context
What this study did
The team compared two ways to run a fixed-interval schedule.
In the standard version a green light tells the participant when the interval starts.
In the response-initiated version the participant’s own button press starts the silent timer.
They watched how fast and how steadily the participants responded under each setup.
What they found
When the participant started the interval, responding jumped early and stayed rapid almost the whole time.
The usual pause after reinforcement shrank and the “scallop” shape almost vanished.
In plain words, letting the learner kick off the timer made their timing sloppy.
How this fits with other research
Schwarz et al. (1970) showed that under a normal FI the sixth response after food sets a steady rhythm.
E et al. found that same rhythm disappears when the learner’s own response starts the clock, so the old rule still holds only if an outside cue marks the start.
Rogers-Warren et al. (1976) added a visible clock to human FI sessions and saw calmer, more efficient responding.
Their result lines up with the new advice: give an external marker when you need precise timing.
KELLEHEBERRYMAELLIOTT et al. (1962) proved that changing the stimulus sequence reshapes FI performance even if the schedule stays the same.
Together these papers show it is the cue, not just the passage of time, that controls accurate fixed-interval behavior.
Why it matters
If you run FI schedules in skill-building or reinforcement labs, decide who starts the interval.
Let the learner start it only when rough timing is okay.
When you need clean scallops or steady pauses, add a clear external signal—light, beep, or spoken word—to mark the start of each interval.
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02At a glance
03Original abstract
Different events can serve as time markers that initiate intervals in schedules of reinforcement. Pigeons were exposed to fixed-interval (FI) schedules in which the onset of the interval was signaled by the illumination of a key light or initiated by a peck to a lighted key. Food was delivered following the first response after the interval elapsed. In Experiment 1, three pigeons were exposed to a multiple schedule. One component was a standard FI schedule: Key light illumination signaled the onset of the interval. The other component was a response-initiated fixed-interval (RIFI) schedule: The first key-peck response determined the onset of the interval. In Experiment 2, three pigeons were exposed to a multiple FI-RIFI schedule of reinforcement and on occasional trials food was not delivered (i.e. "no-food" or "peak trials"). A yoking procedure equated reinforcement rates between the schedule types in both experiments. Absolute response rates early in the intervals were higher in the RIFI schedules of both experiments. Normalized response-rate gradients, ogive fits of normalized response gradients, and breakpoints were not systematically different for the schedule types in Experiment 1, indicating similar patterns of responding between interval onset and food delivery. However, during peak trials in Experiment 2 the duration of responding at a high rate was longer for RIFI schedules than FI schedules. This suggests that timing precision was reduced in the RIFI schedules and that relative "distinctiveness" of a time marker may determine its efficacy.
Journal of the experimental analysis of behavior, 2015 · doi:10.1002/jeab.120