Strategies in probabilistic categorization: results from a new way of analyzing performance

The "Weather Prediction" task is a widely used task for investigating probabilistic category learning, in which various cues are probabilistically (but not perfectly) predictive of class membership. This means that a given combination of cues sometimes belongs to one class and sometimes to another. Prior studies showed that subjects can improve their performance with training, and that there is considerable individual variation in the strategies subjects use to approach this task. Here, we discuss a recently introduced analysis of probabilistic categorization, which attempts to identify the strategy followed by a participant. Monte Carlo simulations show that the analysis can, indeed, reliably identify such a strategy if it is used, and can identify switches from one strategy to another. Analysis of data from normal young adults shows that the fitted strategy can predict subsequent responses. Moreover, learning is shown to be highly nonlinear in probabilistic categorization. Analysis of performance of patients with dense memory impairments due to hippocampal damage shows that although these patients can change strategies, they are as likely to fall back to an inferior strategy as to move to more optimal ones.     

Assessment of interpersonal aggression and violence: introduction to the special issue

Violence and interpersonal aggression are considered major public health problems throughout the world. Yet there is considerable variability in how these terms are operationalized, measured, and studied in the social sciences, which can lead to ambiguity and confusion in the field. In this introduction to the special issue, the authors highlight some of the difficulties inherent in studying interpersonal aggression and violence and briefly review the heterogeneous nature of the research conducted in this area. The authors conclude with a summary of the key findings of the articles that appear in this special issue.     

Further exploration of the Vedic Personality Inventory: validity, reliability and generalizability

The purpose of this study was to explore the validity, reliability, and generalizability of the Vedic Personality Inventory which consists of constructs derived from the Vedic literature of India. There were 57 participants (20 men, 37 women). The mean age was 44.3 yr. (SD= 15.1). The sample was predominantly older, well-educated women who volunteered to participate as respondees to invitations to participate posted in supermarkets, churches, colleges, and on the internet. Analysis yielded statistically significant correlations for scores on the Vedic Personality Inventory and on the Daily Spiritual Experiences Scale and the Brief Symptom Inventory, each of which measures domains of interest addressed by the first inventory.     

Stimulus and response chunking in the Hebb Digits task

Using the Hebb Digits task, an incidental sequential learning paradigm, the effects of chunking of both the presentation and response phases of performance were examined. In the first experiment, consistent stimulus chunking increased learning, and performance was at an equivalent level to this when consistent chunking of both stimuli and responses was present. Consistent chunking of the responses alone did not significantly improve learning over a baseline condition where neither stimuli nor responses were chunked. The disruption of response organization in a second experiment, through a random response condition, failed to impact learning in non-chunked and stimulus chunked conditions. A third experiment found that response chunking did benefit learning in a condition where stimuli were presented in random chunks. A final experiment suggested extended processing of the digits could not account for performance gains in the stimulus chunking condition. Overall, the results suggest that the enhanced effects of chunking on learning were stimulus-driven rather than response-driven, except under conditions that constrained a consistent pattern of stimulus organization.