Studies of operant and reflexive key pecks in the pigeon.
Peck length, not just rate, tells reflexive from operant—watch response form.
01Research in Context
What this study did
Stolz (1977) watched pigeons peck a key under three different schedules.
The team measured how long each peck lasted, not just how often it happened.
They wanted to see if peck length could split reflexive pecks from operant ones.
What they found
Peck length changed in a clean, orderly way when the schedule changed.
Short, stiff pecks looked reflexive. Longer, flexible pecks looked operant.
The same bird could do both kinds, proving one response can have two subclasses.
How this fits with other research
Rapport et al. (1982) later showed pigeons can tell if their last move was a peck or a pause. This builds on B’s idea that birds notice their own behavior.
Adams (1980) found pigeons also track how many pecks they just did. Together these papers say topography, count, and timing all matter.
Palya (1985) pushed the idea further, turning pecks into tacts and mands. Once you know pecks can split, you can bring them under verbal control.
Why it matters
Stop counting only responses per minute. Watch how the response looks and feels. A short, choppy hand flap might be reflexive, while a long, deliberate one could be operant. Reinforce the form you want, not just the rate you want.
Want CEUs on This Topic?
The ABA Clubhouse has 60+ free CEUs — live every Wednesday. Ethics, supervision & clinical topics.
Join Free →Film one target response and time its duration across three sessions—see if form shifts with schedule changes.
02At a glance
03Original abstract
The duration of pigeons' key pecks was studied in three experiments. Experiment I revealed that key pecks early in exposure to continuous reinforcement were of short duration, as were key pecks observed on an omission procedure in which pecks prevented food delivery. Key pecks later in exposure to continuous reinforcement, and those that occurred on positive automaintenance procedures, were of long duration. In Experiment II, pigeons were exposed to fixed-interval and fixed-ratio reinforcement schedules, and durations were recorded separately for each quarter of each interval or ratio. On fixed interval, durations were shorter in the first quarter of each interval than in subsequent quarters; on fixed ratio, durations were longer in the first quarter of the ratio than in subsequent quarters. These data parallel observations of concurrent operant responding and salivation in dogs. In Experiment III, pigeons were exposed to a discrete trial, differential-reinforcement-of-low-rate 6-sec schedule. Durations of responses in the first 2 sec of the trial were substantially shorter than those of responses that occurred later. The data from all three experiments support the view that the pigeon's "key peck" actually consists of two subclasses of peck, one reflexive and one operant.
Journal of the experimental analysis of behavior, 1977 · doi:10.1901/jeab.1977.27-301