The content of compound conditioning

Abstract

In three experiments using Pavlovian conditioning of magazine approach, rats were trained with a compound stimulus, AB, and were concurrently trained with stimulus B on its own. The reinforcement rate of B, rB, was either ½, ⅔, or ⅖ of rAB. After extended training, the conditioning strength of A was assessed using probe trials in which A was presented alone. Responding during A was compared with that during AB, B, and a third stimulus, C, for which rC = rAB – rB. In each experiment, the rats’ response rate during A was almost identical to that during C (and during B, when rB = ½rAB). This suggests that, during AB conditioning, the rats had learned about rA as being equal to [rAB – rB], and implies that the content of their learning was a linear function of r. The findings provide strong support for rate-based models of conditioning (e.g., Gallistel & Gibbon, 2000). They are also consistent with the associative account of learning defined in the Rescorla-Wagner (1972) model, but only if the learning rate during reinforcement equals that during non-reinforcement.