Operant conditioning of a small-scale muscle response.

One adult sat in a quiet lab. Electrodes on the thumb pad picked up the tiniest flicker of muscle electricity.

Each time the signal landed in a preset microvolt window, a pointer on a screen moved. That small visual payoff served as the reinforcer.

The person was never told what made the pointer go; the goal was to see if reinforcement alone could shape a response too small to feel.

The target muscle potentials grew stronger and hit the goal window more often.

Nearby voltage sizes also shifted, showing the change spread across the whole muscle.

The subject never reported noticing the thumb activity, proving the response stayed below conscious awareness.

Weiss (1968) later repeated the trick with monkey eye movements, giving a conceptual replication. Nevin (1968) showed monkeys could time their responses within 50 ms windows, another micro-level feat.

CROSS et al. (1962) had already mapped how response probability and latency move together during stimulus generalization. Bloomfield (1966) adds muscle amplitude to that list, showing all three properties obey the same operant law.

Mann et al. (1971) brought skin resistance under stimulus control, a cousin study that extends the reach of operant methods from skeletal to autonomic micro-responses.

If a response you cannot feel can still be reinforced, you can shape subtle behaviors clients may not notice. Think of micro-movements during handwriting, faint facial tics, or early signs of tension. Use immediate, concrete feedback—lights, clicks, game points—and reinforce the exact micro-response you want. The change can generalize to nearby muscle groups, giving you bonus improvement for free.