When 2 cues occur together and reliably predict an outcome, Ss often judge the effect of the compound as reducible to the individual effects of the elements. This elemental processing in predictive learning is perhaps the single most important aspect of most theories of human inference. Surprisingly, selectional processing was not observed in either blocking or conditioned inhibition problems. Only when the learner had past experience with another problem encouraging an elemental strategy were the expected selectional processes observed. These proactive effects of prior learning were abolished if the earlier problem required a nonadditive solution. The results suggest that configural cues were guiding predictive inferences in the absence of elemental processes.Many authors have been struck by the formal similarity of the problem of covariation detection in humans and animals (e.g., Gluck & Bower, 1988;Holyoak, Koh, & Nisbett, 1989;Shanks & Dickinson, 1987). Both organisms must learn to detect regularities in their environment and to take appropriate actions. That is, predictive signals must be identified in a stream of irrelevant cues, whether these signals predict the romantic interest of another person or patches of food for a hungry animal. These parallels raise the intriguing possibility that similar learning mechanisms may explain how humans and animals solve formally analogous problems.This possibility is encouraged when variables in the human and animal domains have corresponding effects. For example, in assessing the contingency between an action and an outcome, people are sensitive to the likelihood of the outcome in the presence versus absence of the action (e.g., Chatlosh, Neunaber, & Wasserman, 1985). The outcome is presumed to be contingent only if the action influences the background rate of occurrence of the outcome. By no means are the reported contingency effects equivalent to statistical measures of covariation. People often overestimate zero contingencies, especially if there is a high probability of the outcome (Alloy & Tabachnik, 1984). Animals show a similar sensitivity to contingency (Rescorla, 1968) and also respond inappropriately early in training when there is a nominal zero contingency (e.g., Benedict & Ayres, 1972). Shared imperfections in covariation detection like these can be explained by an associative model (e.g., Wasserman, Elek, Chatlosh, & Baker, 1993).Although there has been considerable progress in our understanding of the cognitive processes underlying predictive

In a sample of 208 Holtzman-descended albino rats, we found evidence with 4 measures of conditioning (freezing, defecation, side crossing, and nose crossing) that a single 2-s, 1.0-mA immediate shock could condition fear to a context (Experiments 1, 2, and 4). When we reduced the shock intensity to 0.5 mA, we obtained a complete immediate-shock conditioning deficit according to all measures in Experiment 3 and to all but the defecation measure in Experiment 4. Results suggest two conclusions: (a) Differences in shock potency between laboratories may help explain discrepant findings about whether immediate shock supports contextual conditioning; (b) theories of contextual conditioning need a mechanism that permits that conditioning to result from immediate shock.Recently, considerable interest has developed about understanding the neural and behavioral processes mediating one-trial context fear conditioning (e.g.,

The ability of a blocked or overshadowed conditioned stimulus (CS) to serve as (a) blocker or (b) a 2nd-order reinforcer in Pavlovian fear conditioning was tested in 152 albino rats. CS-evoked suppression of barpressing for food was the index of conditioned fear. Experiments 1 and 2 showed that an overshadowed CS was weakened in its ability to serve as a blocker. In Experiment 2, a blocked CS was similarly weakened. Experiment 3 showed that an overshadowed and blocked CS was weakened in its ability to serve as a 2nd-order reinforcer. Experiments 4 and 5 failed to restore the blocking ability of blocked (Experiment 4) or overshadowed (Experiment 5) CSs by extinguishing the CSs that had blocked or overshadowed them. Results favor a learning-deficit view of blocking and overshadowing.

In three experiments, using a total of 120albino rats, we assessed whether transportation cues might evoke some of the freezing (i.e., defensive immobility) that we see in a context on a day following a footshock given immediately after placement in that context. The results suggested that immediate shock could directly condition strong fear to both simulated and actual transport cues. Although conditioning to transport cues explains some ofthe freezing that is seen on the test day, it does not explain all of it. Wealso found evidence that some of the freezing is due to conditioning to permanent features of the context in which the immediate shock is given. The results support a role for transport cues in theories of context conditioning and argue against shock-processing accounts of the conditioning deficit that results from immediate shock A rat is placed in a box and given a single brief shock. On the next day it is returned to the box and its behavior is examined. The behavior is found to consist in part of freezing (i.e., defensive immobility). Such freezing is regarded as an index of fear, classically conditioned to the box or context. The amount offreezing depends critically on the time interval between placement and shock. The freezing is weak if the interval is very short (0-15 sec) and grows stronger as the interval lengthens (e.g., 45-135 sec); it weakens again as the interval increases further

In each of two experiments, we studied Pavlovian fear conditioning (as assessed by barpress conditioned suppression) in 32 albino rats. Following a two-stage cue-competition procedure (A+ then AX+), we subjected the competing cue (A) to conditioned inhibition training (B+, BA-) before testing the target cue (X). Conditioned inhibition training was designed to weaken the putative A-unconditioned stimulus (US) association, perhaps changing it to an A-no-US association. Performance-deficit theories of cue competition, such as comparator theory and retrieval-interference theory, predict that such procedures should weaken cue competition, causing Conditioned Stimulus X (CS X) to evoke strong responding. The same prediction can be deduced from recent acquisition-focused models (Dickinson & Burke, 1996;Van Hamme & Wasserman, 1994). In opposition to this prediction, however, we found in both experiments that conditioned inhibition training had no detectable effect on cue competition even though it successfully abolished conditioned responding to CS A. In Experiment 2, moreover, we found evidence against the hypothesis that the weak response to CS Xwas due to generalization decrement rather than to cue competition. Results favor early learning-deficit theories of cue competition over performance-deficit theories and over the recent acquisition-focused models.