Positive behavioral contrast in 3-month-old infants on multiple conjugate reinforcement schedules.
Three-month-old babies kick harder when reinforcement stops in another part of the session, proving behavioral contrast starts early in life.
01Research in Context
What this study did
Researchers tested three-month-old babies on a two-part schedule. One part let the babies kick to make a crib mobile move. The other part stopped the mobile even when the babies kicked.
Each baby lay in the crib with a soft band around one foot. Kicks pulled a string that spun colorful toys overhead. After many sessions the team switched the rules. Now the mobile only worked in one part of the schedule.
What they found
When the mobile stopped working in one part, the babies kicked even harder in the part that still worked. This jump in kicks is called positive behavioral contrast.
The effect showed up quickly and stayed strong across sessions. Even tiny infants can show the same contrast seen in adult animals.
How this fits with other research
Hineline et al. (1969) first saw contrast in pigeons. They found that upcoming extinction boosts responding in the prior reinforced part. The infant study mirrors this pattern, proving the effect is not limited to birds.
Sadowsky (1973) showed that timeout or blackout, not just extinction, can drive contrast. The infant work adds humans to that list, showing the effect is robust across very different species and reinforcers.
Ginsburg et al. (1971) showed longer extinction periods create bigger contrast. The infant study did not test duration, but it confirms that even brief extinction is enough to produce the jump in responding.
Why it matters
You now know that contrast can appear as early as three months. When you run multiple-schedule programs, expect jumps in correct responses whenever another part of the session turns lean. Use this to your advantage: insert brief extinction or timeout periods to boost motivation in reinforced parts, but watch for over-kicking or other intense responses that might wear clients out.
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02At a glance
03Original abstract
Positive behavioral contrast was assessed in two experiments with young infants using multiple conjugate reinforcement schedules. Reinforcement was produced by footkicks which activated the objects of an overhead crib mobile in a manner proportional to the vigor and rate of responding. Distinctive color/pattern cues on the sides of the objects served as discriminative stimuli for components of the multiple schedule. In Experiment 1, infants were trained with one cue (S+) only before insertion of S+ into a multiple schedule with an extinction component. A control group received S+ throughout all sessions. In Experiment 2, a multiple schedule was introduced at the outset, and responses in both components were reinforced before the introduction of extinction in the second component. In a final phase, reinforcement was reintroduced into the second component. Positive behavioral contrast occurred in both experiments. Response reduction in the extinction component was seen only in individual relative response curves. In both experiments, negative emotional behaviors accompanied the extinction component, and in Experiment 1, cooing accompanied presentations of S+.
Journal of the experimental analysis of behavior, 1979 · doi:10.1901/jeab.1979.32-15