What important factor in learning is Rescorla best known for?

Robert A. Rescorla is best known for his work on the role of contingency in classical conditioning, which is an important factor in learning. His research, particularly the Rescorla-Wagner model developed with Allan Wagner, provided a deeper understanding of how stimuli are associated with outcomes and how the strength of learning is influenced by the predictability of an unconditioned stimulus following a conditioned stimulus.

Prior to Rescorla's work, classical conditioning was largely understood through the lens of temporal association, where it was believed that the mere pairing of two stimuli in time was sufficient for learning to occur. However, Rescorla's experiments demonstrated that the contingency between the conditioned stimulus (CS) and the unconditioned stimulus (US) is critical. This means that the CS must reliably predict the US for the conditioning to be strong.

Rescorla's research showed that if the CS is sometimes presented without the US, or if the US is also presented without the CS, the learning is much weaker. This finding led to a shift in the understanding of classical conditioning, emphasizing the importance of the informational content of the CS about the US, rather than just the temporal pairing.

The Rescorla-Wagner model quantitatively describes the process of classical conditioning, proposing that the strength of learning is proportional to the surprise of the US. If the US is fully predicted, no learning occurs, whereas unexpected US presentations lead to stronger learning. This model has been influential in the field of learning and has implications for understanding a wide range of learning processes in both animals and humans.