The role of verbal behavior in human learning: infant performance on fixed-interval schedules.
Preverbal infants on fixed-interval schedules act like animals, showing that language later reshapes human timing behavior.
01Research in Context
What this study did
Two babies, not yet talking, sat in a lab. A red light came on every 30 seconds. If they pressed a button when the light was on, they got a tiny bit of applesauce or a short lullaby.
The team watched how the babies spaced their presses across many 30-second cycles. They wanted to see if the infants would act like rats or like older children.
What they found
Both babies pressed fastest right before the 30-second mark, then paused. This scallop shape matches pigeon and rat data.
Older humans usually show steady, fast pressing once they can say 'I have to wait.' These babies could not say that yet, so they behaved like animals.
How this fits with other research
Schmidt et al. (1969) saw the same scallop in adults, but only when the adults had no instructions. Adding rules made the scallop vanish. The infant data fit this rule: no words, no rules, animal curve.
Migler et al. (1969) also failed to find scalloping in rabbits. The rabbit and infant results line up—both groups lack the verbal tools that flatten the curve.
Bulla et al. (2026) later showed that limiting how often people can respond speeds learning. Their work keeps the theme alive: the way we let people respond changes what the schedule does.
Why it matters
If a client cannot yet talk or follow rules, expect animal-like schedule effects: long pauses followed by bursts. Use short, rich reinforcement instead of long fixed waits. When language grows, teach self-rules like 'wait a bit' to smooth out responding.
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02At a glance
03Original abstract
The performances of two infants less than one year old were investigated on fixed-interval schedules. When the infants touched a cylinder either music or food was presented according to fixed-interval schedules ranging in value from 10 to 50 seconds. With respect to two principal criteria, namely, pattern of responding and sensitivity to the schedule parameter, the subjects' behavior closely resembled that of animals but differed markedly from that of older children and adults. Negatively accelerated responding in the course of the fixed interval in the early sessions gave way to a scalloped pattern, consisting of a pause after reinforcement followed by an accelerated response rate. This scalloped pattern was the final form of responding on all schedule values. Analysis of data after performance had stabilized showed that postreinforcement pause was a negatively accelerated increasing function, and running rate (calculated after excluding the postreinforcement pause) was a declining function, of schedule value. On each schedule, the durations of mean successive interresponse times declined in the course of the fixed interval and were directly related to schedule value. The results supported Lowe's (1979) suggestion that verbal behavior may be responsible for major differences in the schedule performance of older humans and animals.
Journal of the experimental analysis of behavior, 1983 · doi:10.1901/jeab.1983.39-157