Two views have dominated theories of deductive reasoning. One is the view that people reason using syntactic, domain-independent rules of logic, and the other is the view that people use domain-specific knowledge. In contrast with both of these views, we present evidence that people often reason using a type of knowledge structure termed prngmutic r-eusoning schemas. In two experiments, syntactically equivalent forms of conditional rules produced different patterns of performance in Wason's selection task, depending on the type of pragmatic schema evoked. The differences could not be explained by either dominant view. We further tested the syntactic view by manipulating the type of logic training subjects received. If people typically do not use abstract rules analogous to those of standard logic, then training on abstract principles of standard logic alone would have little effect on selection performance, because the subjects would not know how to map such rules onto concrete instances. Training results obtained in both a laboratory and a classroom setting confirmed our hypothesis: Training was effective only when abstract principles were coupled with examples of selection problems, which served to elucidate the mapping between abstract principles and concrete instances. In contrast, a third experiment demonstrated that brief abstract training on a pragmatic reasoning schema had a substantial impact on subjects' reasoning about problems that were interpretable in terms of the schema, The dominance of pragmatic schemas over purely syntactic rules was discussed with respect to the relative utility of both types of rules for solving real-world problems.

Previous work has suggested that human subjects engaged in tasks, like the Stroop task, that require response selection utilize the medial frontal cortex. We used positron emission tomography to measure blood flow changes in a stimulus-response compatibility task designed to maximize the demand on response selection processes. We report significant activation in the cingulate sulcus (Brodman's area 32) and a correlation of activity in this region with faster response time for an incongruent stimulus-response task.

Building upon earlier behavioral models of animal and human learning, we explore how a psychobiological model of animal conditioning can be applied to amnesic category learning. In particular, we show that the late-training deficit found in Knowlton, Squire, and Gluck's 1994 study of amnesic category learning can be understood as a natural consequence of Gluck and Myers's (1993) theory of hippocampal-region function, a theory that has heretofore been applied only to studies of animal learning. When applied to Knowlton et al.'s category learning task, Gluck and Myers's model assumes that the hippocampal region induces new stimulus representations over multiple training trials that reflect stimulus-stimulus regularities in the training set. As such, the model expects an advantage for control subjects over hippocampal-damaged amnesic patients only later in training when control subjects have developed new hippocampal-dependent stimulus representations; in contrast, both groups are expected to show equivalent performance early in training. A potentially analogous early/late distinction is described for animal studies of stimulus generalization. Our analyses suggest that careful comparisons between early and late-training differences in learning may be an important factor in understanding 3Corresponding author. amnesia and the neural bases of both animal and human learning.

Although most analyses of amnesia have focused on the loss of explicit declarative and episodic memories following hippocampal-region damage, considerable insights into amnesia can also be realised by studying hippocampal function in simple procedural, or habit-based, associative learning tasks. Although many simple forms of associative learning are unimpaired by hippocampal damage, more complex tasks which require sensitivity to unreinforced stimuli, configurations of multiple stimuli, or contextual information are impaired by hippocampal damage. In several recent papers we have developed a computational theory of hippocampal function which argues that this brain region plays a critical role in the formation of new stimulus representations during learning (Gluck & Myers, 1993, 1995; Myers & Gluck, 1996; Myers, Gluck, & Granger, 1995). We have applied this theory to a broad range of empirical data from studies of classical conditioning in both intact and hippocampal-lesioned animals, and the model correctly accounts for these data. The classical conditioning paradigm can be adapted for use in humans, and similar results for acquisition are obtained in both normal and hippocampal-damaged humans. More recently, we have begun to address an important set of category learning studies in both normals and hippocampal-damaged amnesics. This work integrates experimental studies of amnesic category learning (Knowlton, Squire, & Gluck, 1994) with theoretical accounts of associative learning, and builds on previously established behavioural correspondences between animal conditioning and human category learning (Gluck & Bower, 1988a). Our work to date illustrates some initial progress towards a more integrative understanding of hippocampal function in both animal and human learning, which may be useful in guiding further empirical and theoretical research in human memory and amnesia.

Learning that one cue (CS) predicts a second, salient cue (US) can often be slowed by prior exposure to one or both stimuli. In animals, CS±US learning is more strongly retarded following uncorrelated exposure to both CS and US than following exposure to the US alone. In this paper we present several studies showing a similar effect in humans, using a computer-based task. Experiments 1 and 2 used a between-groups design and demonstrated a strong CS/US exposure effect, whether or not the US was signalled by a neutral cue during exposure. Experiment 3 demonstrated similar effects using a within-subjects design. Overall, these results are consistent with several theoretical interpretations and suggest that uncorrelated CS/US exposure leads to a robust retardation of subsequent CS±US learning in humans.