Time as content in Pavlovian conditioning.

Time has played only a limited role within the traditional theories of Pavlovian conditioning. Although temporal factors certainly contribute to whether conditioning occurs, the traditional assumption in the associative framework has been that associations lack temporal information. Recently, the temporal coding hypothesis has challenged that view, arguing that animals encode temporal relationships as part of associations. That is, proximal temporal relationships not only foster associative learning, but also are part of the content of learning. The present paper reviews for the nonspecialist the increasing empirical evidence that temporal coding is ubiquitous in Pavlovian paradigms, including simultaneous and backward conditioning, second-order conditioning, sensory preconditioning, cue competition, Hall-Pearce type CS-preexposure, and conditioned inhibition. The data support the temporal coding hypothesis' view that contiguity is sufficient for associative learning to occur, but challenge the central assumption of the informational hypothesis that predictive relations are necessary for learning to occur (as opposed to predictive relationships only being necessary for the expression of knowledge).