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Rats had a memory loss of a fear response when they received an electroconvulsive shock 24 hours after the fear-conditioning trial and preceded by a brief presentation of the conditioned stimulus. No such loss occurred when the conditioned stimulus was not presented. The memory loss in animals given electroconvulsive shock 24 hours after conditioning was, furthermore, as great as that displayed in animals given electroconvulsive shock immediately after conditioning. This result throws doubt on the assertion that electroconvulsive shock exerts a selective amnesic effect on recently acquired memories and thus that electroconvulsive shock produces amnesia solely through interference with memory trace consolidation.

Manipulative strategies of social conduct (Machiavellianism) have been studied by both psychologists and evolutionary biologists. The authors use the psychological literature as a database to test evolutionary hypotheses about the adaptive advantages of manipulative social behavior. Machiavellianism does not correlate with general intelligence and does not consistently lead to real-world success. It is best regarded as 1 of several social strategies, broadly similar to the "defect" strategy of evolutionary game theory, which is successful in some situations but not others. In general, human evolutionary psychology and evolutionary game theory provide useful frameworks for thinking about behavioral strategies, such as Machiavellianism, and identify a large number of specific hypotheses that have not yet been tested by personality and social psychologists.

Cue competition is one of the most studied phenomena in associative learning. However, a theoretical disagreement has long stood over whether it reflects a learning or performance deficit. The comparator hypothesis, a model of expression of Pavlovian associations, posits that learning is not subject to competition but that performance reflects a complex interaction of encoded associative strengths. That is, subjects respond to a cue to the degree that it signals a change in the likelihood or magnitude of reinforcement relative to that in the cue's absence. Initially, this performance-focused view was supported by studies showing that posttraining revaluation of a competing cue often influences responding to the target cue. However, recently developed learning-focused accounts of retrospective revaluation have revitalized the debate concerning cue competition. Further complicating the picture are phenomena of cue facilitation, which have been addressed less frequently than cue competition by formal models of conditioning of either class. The authors present a formalization and extension of the comparator hypothesis, which results in sharpened differentiation between it and the new learning-focused models.

The Rescorla-Wagner model has been the most influential theory of associative learning to emerge from the study of animal behavior over the last 25 years. Recently, equivalence to this model has become a benchmark in assessing connectionist models, with such equivalence often achieved by incorporating the Widrow-Hoff delta rule. This article presents the Rescorla-Wagner model's basic assumptions, reviews some of the model's predictive successes and failures, relates the failures to the model's assumptions, and discusses the model's heuristic value. It is concluded that the model has had a positive influence on the study of simple associative learning by stimulating research and contributing to new model development. However, this benefit should neither lead to the model being regarded as inherently "correct" nor imply that its predictions can be profitably used to assess other models.

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Forward blocking is one of the best-documented phenomena in Pavlovian animal conditioning. According to contemporary associative learning theories, forward blocking arises directly from the hardwired basic learning rules that govern the acquisition or expression of associations. Contrary to this view, here the authors demonstrate that blocking in rats is flexible and sensitive to constraints of causal inference, such as violation of additivity and ceiling considerations. This suggests that complex cognitive processes akin to causal inferential reasoning are involved in a well-established Pavlovian animal conditioning phenomenon commonly attributed to the operation of basic associative processes. Keywordsanimal conditioning; cue competition; causal reasoning; associative learning; animal cognition Ever since the seminal experimental studies with dogs by Pavlov (1927), research into classical conditioning has been flourishing more or less constantly, surviving shifts of paradigm from behaviorism to cognitivism, connectionism, and behavioral neuroscience. Along the way, it has provided indispensable input to fields as diverse as animal cognition, behavior therapy, human psychophysiology, stereotyping in social psychology, back-propagation models of parallel distributed processing, and basic neuroscience.In Pavlovian conditioning, an initially neutral conditioned stimulus (CS; e.g., a tone) comes to elicit a conditioned response (e.g., freezing) as the result of pairings of the CS with a biologically relevant, unconditioned stimulus (US; e.g., a footshock). Very basic and relatively simple associative principles have often been assumed to account for such Pavlovian

Recent research suggests that outcome additivity pretraining modulates blocking in human causal learning. However, the existing evidence confounds outcome additivity and outcome maximality. Here the authors present evidence for the influence of presenting information about outcome maximality (Experiment 1) and outcome additivity (Experiment 2) on subsequent forward blocking. The results of Experiment 3 confirm that, with outcome maximality controlled, outcome additivity affects backward blocking but not release from overshadowing. Finally, the results of Experiment 4 demonstrate that information about outcome additivity has a similar effect on forward blocking if presented after the blocking training instead of before. The results are compatible with the idea that blocking results from inferential processes at the time of testing and not from a failure to acquire associative strength during training.