Reinforcing saccadic amplitude variability.
Motor variability is an operant dimension you can turn up or down with simple differential reinforcement.
01Research in Context
What this study did
Céline et al. (2011) asked adults to move their eyes from dot to dot on a screen.
Each time the size of the eye jump varied, the computer paid a penny.
When steady jumps were paid instead, the swings shrank back to baseline.
What they found
Money for variable eye jumps doubled the spread of jump sizes.
The middle jump size stayed the same—only the scatter grew.
When the rule flipped, scatter snapped back, proving the change was operant.
How this fits with other research
Dougherty et al. (1996) saw the same thing in rats: lever-press variability rose or fell with the payoff rule.
Gerow et al. (2019) used the same differential-reinforcement trick to shrink repetitive hand flaps in a toddler.
Lancioni et al. (2009) shaped new hand moves while cutting spastic ones, showing the principle works across disabilities.
Together the four papers say: if you can count it, you can reinforce more or less of it—eyes, hands, or paws.
Why it matters
You can sculpt motor variability on the fly. Want a client to explore new reaching paths? Reinforce any path that differs from the last. Want to lock in a steady grasp? Pay only for repeats. No extra toys or drugs—just clear contingencies.
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02At a glance
03Original abstract
Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we reinforced the least frequent saccadic amplitudes to increase variability, and then reinforced the central part of the amplitude distributions to reduce variability. The target was placed at a constant distance from the fovea after the saccade to maintain the postsaccadic visual signal constant and an auditory reinforcement was delivered depending on saccadic amplitude. The second experiment tested the effects of the contingency. We reinforced high levels of variability in 4 participants, whereas 4 other participants were assigned to a yoked control group. On average, saccadic amplitude standard deviations were doubled while the medians remained mostly unchanged in the experimental participants in both experiments, and variability returned to baseline level when low variability was reinforced. In the control group no consistent changes in amplitude distributions were observed. These results, showing that variability can be reinforced, challenge the idea of a stochastic neural noise. We instead propose that selection processes constrain saccadic amplitude distributions.
Journal of the experimental analysis of behavior, 2011 · doi:10.1901/jeab.2011.95-149