THE SUCCESSIVE DIFFERENTIATION OF A LEVER DISPLACEMENT RESPONSE.
Shrink the reward zone step by step to sculpt precise movements, but stop before the zone gets so small that learning freezes.
01Research in Context
What this study did
The team worked with rats pressing a lever.
They started by rewarding any press.
Then they shrank the reward zone bit by bit.
The goal was to shape how far the lever moved.
What they found
The rats' presses landed closer together as the zone narrowed.
Most presses hit the bottom edge of each new zone.
When the zone got too small, progress stopped.
The rats could not get more precise beyond that point.
How this fits with other research
Jenkins et al. (1973) also shaped tiny lever differences, but looked at speed, not distance.
Reed (2003) later showed that a short beep can speed or slow the next press, depending on how fast the rat was going before the beep.
Ross et al. (2002) found that delaying after-session snacks makes pressing stronger and harder to disrupt.
All these rat-lever studies keep showing the same lab truth: small changes in when or how you deliver rewards fine-tune behavior in big ways.
Why it matters
You can tighten a response the same way with kids.
Start by rewarding wide tries, then only reward closer and closer matches.
Watch for the plateau: if progress stalls, the zone may be too small; back up and widen it again.
This keeps shaping smooth and keeps motivation high.
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Join Free →Widen the current response criterion by one centimeter, then bring it back down one millimeter at a time across trials.
02At a glance
03Original abstract
Maximum displacements of lever presses by rats were recorded under eight successively-smaller reinforcement zones (RZ). The largest RZ included displacements from 3 degrees to 44 degrees ; the smallest, from 24 degrees to 29 degrees . As the RZ decreased, displacement distributions reflected a least-effort tendency: distributions peaked at the lower limit of RZ and most non-reinforced presses fell just below the lower limit. Successive distributions (a) differed significantly in shape, (b) showed reduced variability, and (c) indicated more presses and more presses per reinforcement. Prolonged training under the smallest RZ gave no improvement in performance.
Journal of the experimental analysis of behavior, 1964 · doi:10.1901/jeab.1964.7-211