Compounding of discriminative stimuli correlated with chained and multiple schedules.

Cohen (1975) tested what happens when you combine two stimuli that signal different schedules. The rats pressed a lever. Sometimes a light meant food, sometimes a tone meant food. The team then turned on both cues together.

They used chained and multiple schedules. They also tried fixed order and free food. They wanted to see if the old rules about random order and tight contingencies really mattered.

When both cues came on at once, lever presses jumped higher than with either cue alone. The rise looked like simple addition. The boost stayed even when the order was fixed or when food no longer needed a press.

So the big idea held: compounding gives summation. The extra safeguards were not needed.

Macdonald (1973) showed the same summation two years earlier, but kept the order random. The new study keeps the summation while dropping that safeguard.

Dove et al. (1974) saw both rises and falls in chained schedules. The 1975 paper narrows it down: terminal compounds add, initial ones can add too if the schedule is right.

Cohn et al. (2007) later copied the effect with tone plus smell. The summation travels across senses.

Grey et al. (2024) brings the check to match-to-sample. They warn us to test each part of a compound so we know the learner sees the whole, not just one piece.

You can build stronger stimulus control by pairing cues. Put the red card with the bell, not just one or the other. The boost still works even if you fix the order or give free praise. When you write a chained schedule, think about where you place the compound. Terminal links give the clearest summation. Before calling a compound a single stimulus, probe each part. These moves make teaching faster and more robust for kids with autism or other learners.