Associative and behavior systems accounts of Pavlovian conditioning have different emphases. The traditional associative account has focused on the role of the unconditional stimulus (US) in strengthening stimulus associations according to a set of general laws. The behavior systems account has focused on the relation of conditional responding to the preorganized perceptual, motor, and motivational organization engaged by the US. Knowledge of a behavior system enables successful prediction of the form and ease of conditioning as a function of the type of conditional stimulus (CS), US, and the CS-US relation. At the same time, Pavlovian manipulations act as a window on how a behavior system works. Both associative and behavior systems accounts can be criticized as incomplete and idiosyncratic. A comprehensive account of Pavlovian conditioning could profit from their integration.
405Laboratory-associationist and adaptive-evolutionary accounts of Pavlovian conditioning differ markedly in their focus. The former has emphasized the association between the conditional stimulus (CS) and the unconditional stimulus (US), and the role of the US in strengthening it (e.g., Hearst, 1988;Kimble, 1961;Mackintosh, 1974;Pavlov, 1927). Conditioning procedures have been refined and standardized to isolate the study of associations from the influence of instincts, nonassociative changes, and response-contingent reward (Hilgard & Marquis, 1940;Kimble, 1961). More recent models have expanded the types ofassociation and the role ofcontext, multiple CSs, the CS-US contingency, and stimulus representations in determining behavior (e.g., Miller & Matzel, 1988;Rescorla & Holland, 1982). However, the focus has remained on associations among stimuli and the simple causal role of the US. Within this approach, behavior has been treated primarily as an index of the strength of associations.In contrast, adaptive-evolutionary accounts of Pavlovian conditioning have emphasized behavior, especially the relation of the conditional response to the form and orientation of naturally occurring functional behavior and relevant underlying structure and processes (e.g., Davey, 1989;Fanselow & Lester, 1988;Gardner & Gardner, 1988;Holland, 1984;Hollis, 1982Hollis, , 1990Konorski, 1967;Rozin & Schull, 1988;Timberlake, 1983b;Timberlake & Lucas, 1989; Timberlake & Silva, in press). In this approach, establishing the perceptual-motor organiCompletion of this manuscript was facilitated by NIMH Grant 37892 and NSF Grant IBN 91 21647. The manuscript is based on a symposium presentation at the meetings of the American Psychological Association, Toronto, 1993. I am indebted to Cynthia Langley, Fran Silva, and Kathleen Silva for their comments. Please address correspondence to W. Timberlake, Department of Psychology, Indiana University, Bloomington, zation and motivational processes underlying behavior is a critical step in understanding conditioning. Presentation of the US is viewed as engaging and constraining preorganized mechanisms underlying behavior, rather tha...