Accounts of decision-making have long posited the operation of separate, competing valuation systems in the control of choice behavior. Recent theoretical and experimental advances suggest that this classic distinction between habitual and goal-directed (or more generally, automatic and controlled) choice may arise from two computational strategies for reinforcement learning, called model-free and model-based learning. Popular neurocomputational accounts of reward processing emphasize the involvement of the dopaminergic system in model-free learning and prefrontal, central executive-dependent control systems in model-based choice. Here we hypothesized that the hypothalamic-pituitaryadrenal (HPA) axis stress response-believed to have detrimental effects on prefrontal cortex function-should selectively attenuate model-based contributions to behavior. To test this, we paired an acute stressor with a sequential decision-making task that affords distinguishing the relative contributions of the two learning strategies. We assessed baseline working-memory (WM) capacity and used salivary cortisol levels to measure HPA axis stress response. We found that stress response attenuates the contribution of model-based, but not model-free, contributions to behavior. Moreover, stress-induced behavioral changes were modulated by individual WM capacity, such that low-WM-capacity individuals were more susceptible to detrimental stress effects than high-WMcapacity individuals. These results enrich existing accounts of the interplay between acute stress, working memory, and prefrontal function and suggest that executive function may be protective against the deleterious effects of acute stress.A number of accounts of human and animal decision-making posit the coexistence of separate valuation systems that control choice (1-4), which, broadly speaking, represent automatic or habitual vs. deliberative or controlled modes. The circumstances under which one system may dominate over the other and thereby exert control over behavior has been a question of interest in both neuroscience and psychology, in part because of the implications of such differential control for disorders of compulsion such as drug abuse (5, 6). Acute stress may afford unique leverage in isolating the properties of these systems, because it is believed to prompt a shift from more cognitive or deliberative processes to more automatic processes presumed to be underpinned by phylogenetically older brain structures (7).Accordingly, a spate of recent work suggests that acute stressindexed by changes in levels of cortisol, a neuroendocrine marker of stress response-engenders reliance on putative habitual and/ or automatic processes in human decision-making (8-13), consistent with the assumption that the physiological stress response impairs central executive functions subserving more deliberative choice. However, distinguishing such processes is both experimentally and theoretically fraught, because in dual process theories, which system controls a particular behavior is t...

An experiment was conducted to investigate individual differences and interrelationships in performance on three short-term memory processing and visual processing tasks. Parameters of models for these tasks were correlated. High correlations (.97 and .&1) were obtained for some intertask parameters, indicating that elemental component processes for different tasks can be identified that are similar or highly related. Psychometric measures (SATM and SATV) were also correlated with the information processing model parameters. High multiple correlations of SATV and SATM were obtained using model parameters as predictors, when the data were analyzed separately for female and male subjects. The results are suggestive of sex differences in the interrelationships of the cognitive processes under investigation.