Behavioral interactions and stimulus control during conditional discriminations.

Wilkie (1973) worked with pigeons in a lab. The birds had to pick one key when a line was tilted and a house light blinked fast, and another key when the same line was tilted but the light blinked slowly.

The twist: only one dimension mattered at first. Later, both had to be watched to win food. The team tracked which cue the birds actually used.

When food came for watching just one cue, the pigeons ignored the other. Full control by both line tilt and blink speed showed up only after the schedule required noticing both.

In plain words, if you reward only part of the picture, learners stick to that part.

Blough (1971) showed the same birds could use line tilt only when a red light was on, proving conditional control exists. The 1973 paper adds the rule: reinforcement must demand both cues or control stays lopsided.

Paul et al. (1987) later found that switching problems each day helped pigeons lock in this two-cue control. Together the studies say: first make both cues pay off, then rotate contexts to keep the skill solid.

Striefel (1972) warned that big differences in one dimension can hide small ones. Wilkie (1973) answers that risk by tying food to both dimensions, forcing the birds to notice everything.

When you teach conditional discriminations—like pointing to ‘cat’ only on a red background—check that your reinforcement plan rewards the whole compound, not just the easiest cue. If you see a learner stuck on one feature, pause and require both before delivery. This small shift builds fuller stimulus control and cuts later errors.