OVERT "MEDIATING" BEHAVIOR DURING TEMPORALLY SPACED RESPONDING.

Scientists watched rats work on a DRL 72-second schedule. The rat had to wait at least 72 seconds between lever presses to earn food.

They wanted to see what the rat would do during the long wait. No extra cues or prompts were given.

Each rat started to bite its own tail while the clock ran. The tail biting showed up at the same moment every trial.

Because the biting filled the pause, the rat pressed the lever at the right time and got more food. The stereotypy worked like a homemade timer.

Hart et al. (1974) later ran a similar DRL study. When the schedule got even longer, tail biting was replaced by fast wheel running. Same idea — the rat fills the wait — but a new movement took over.

HEARSKELLEHER et al. (1964) showed that DRL schedules flatten stimulus generalization curves. Together the papers say DRL does not just slow responding; it also changes what the animal feels, sees, and does.

Fyfe et al. (2007) proved that stereotypy in humans can be brought under stimulus control. The rat tail-biting and the human hand-waving both follow operant rules, so your interventions can target the contingency, not just the topography.

If a client shows odd repetitive movements during DRL or wait-time programs, the behavior may be their own self-made timer. Instead of stamping it out, try measuring whether it helps them hit the interval. You can then shape a quieter mediator, like counting aloud or touching a card, that serves the same function without the stigma.