Waiting in pigeons: the effects of daily intercalation on temporal discrimination.

Researchers tested how pigeons adjust their waiting time when food schedules change every day. They switched between short fixed-interval (FI) schedules—10, 20, or 30 seconds—and one long 300-second schedule. Each new schedule started fresh every morning.

Birds lived in experimental chambers with response keys and grain feeders. Sessions ran seven days a week. The team measured how long each bird waited before the first peck after food delivery.

Pigeons quickly matched their wait to the new short interval within one day. When the schedule jumped from 300 s to 10 s, birds shortened pauses right away. But the reverse move failed: after short-interval days, birds could not stretch waits to fit the 300 s schedule.

Short intervals won the fight. Their effect lingered and blocked control by the long interval. Daily swaps worked only when the new FI was 20 s or less.

Rapport et al. (1996) extends these results by showing pigeons can track more complex, sinusoidal patterns of intervals, not just daily steps. The 1992 data act as a building block for the later dynamic work.

Fantino (1969) reported similar stubborn short-interval effects under multiple FI schedules. Early short cycles shortened pauses, matching the 1992 finding that brief intervals dominate timing.

Dougan (1987) adds that even a single preceding interval can nudge current wait time. Together, the studies show timing is swayed by recent history at three scales: trial-by-trial, daily, and patterned cycles.

If you run FI or FI-like reinforcement with learners, remember that short intervals cast a long shadow. After several brief FI days, expect faster responding that may persist even when you stretch the interval. To build longer wait times, insert extra days at moderate lengths or provide clear timing cues to help the new interval win control.