Combined-stimulus control as a function of the response rate controlled by the absence of the single stimuli.

The researchers trained pigeons to peck a key when a light was OFF. They then tested how fast the birds pecked when two lights came on together.

They wanted to see if the birds' earlier peck rate during the dark period would predict how they acted when the paired lights showed up.

The birds that had learned to peck fastest in the dark later pecked slowest when the two lights appeared together.

The birds that had pecked slowly in the dark later pecked faster when the lights were combined. The earlier rate flipped.

Weisman (1970) showed that using a DRO schedule can cut responding to the OFF stimulus. That paper set the stage for the 1972 finding by proving you can shape different rates to stimulus absence.

Neuringer (1973) found that presence-absence training alone gives flat generalization curves. The 1972 study adds that even if control is weak, the exact rate you train to the absence still matters later.

Wildemann et al. (1973) tracked how control curves sharpen over trials. The 1972 paper shows the starting point of those curves is set by the response rate you installed during absence training.

When you run error-correction or teach conditional discriminations, remember the learner's history with the 'no-stimulus' periods. If a child responds a lot during your 'wait' or 'no-reinforcement' intervals, that high rate can later suppress responding when you mix stimuli together. Track rate during absence phases and adjust your next teaching set accordingly.