The Leximancer system is a relatively new method for transforming lexical co-occurrence information from natural language into semantic patterns in an unsupervised manner. It employs two stages of co-occurrence information extraction-semantic and relational-using a different algorithm for each stage. The algorithms used are statistical, but they employ nonlinear dynamics and machine learning. This article is an attempt to validate the output of Leximancer, using a set of evaluation criteria taken from content analysis that are appropriate for knowledge discovery tasks.

Item noise models of recognition assert that interference at retrieval is generated by the words from the study list. Context noise models of recognition assert that interference at retrieval is generated by the contexts in which the test word has appeared. The authors introduce the bind cue decide model of episodic memory, a Bayesian context noise model, and demonstrate how it can account for data from the item noise and dual-processing approaches to recognition memory. From the item noise perspective, list strength and list length effects, the mirror effect for word frequency and concreteness, and the effects of the similarity of other words in a list are considered. From the dual-processing perspective, process dissociation data on the effects of length, temporal separation of lists, strength, and diagnosticity of context are examined. The authors conclude that the context noise approach to recognition is a viable alternative to existing approaches.

We introduce a model to relate the personality dimensions of introversion-extraversion, achievement motivation, and anxiety to efficient cognitive performance. We show how these personality dimensions in combination with situational moderators (e.g., success, failure, time pressure, incentives, time of day, and stimulant drugs) affect the motivational constructs of arousal and effort. We propose a general information-processing model that accounts for the systematic effects of these motivational states on certain task components (sustained information transfer and some aspect of short-term memory). We combine empirical generalizations about task components in a structural model and derive testable predictions that differentiate alternative motivational hypotheses.There are two major approaches to the study of human intellectual performance. The first focuses on the effect of personality and individual differences, and the second attempts toThe order of authorship is arbitrary. This research was supported in part by Grant MH29209(01-04) from the National Institute of Mental Health to both authors, in part by Grant MH29209(05-07) from the National Institute of Mental Health to William Revelle, and in part by a grant from the University of Queensland to Michael Humphreys. Preparation of an earlier draft of the article done at Oxford University was supported in part by Fogarty Senior International Fellowship TW00580 from the National Institutes of Health to William Revelle.We gratefully acknowledge the suggestions and comments made on earlier drafts of this article by K. Anderson, J. Atkinson, D. Birch, D. Broadbent, C. Duncan, H. J. Eysenck, L. Goldberg, J. A. Gray, M. J. Lynch, G. Mandler, J. Onken, T. Rocklin, and B. Underwood. We particularly appreciate the many hours of discussion and criticism given to us by our students. We would also like to thank N. Block, R. Conti, T. Lederer, L. Smith, and R. Shore for their assistance in preparing the various drafts.Requests for reprints should be sent to William Revelle, Department of Psychology, Northwestern University, Evanston, Illinois 60201 or to Michael S. Humphreys, Department of Psychology, University of Queensland, St. Lucia, Brisbane, Queensland, Australia 4067. develop general laws of cognitive psychology or information processing. Although these two approaches rarely are combined, it is difficult to find an example of cognitive performance that is not better understood by a combination of both areas. In this article we propose a theory that integrates these two fundamentally different paradigms.We believe that theoretical and empirical work on at least three personality dimensions poses a problem for anyone interested in the relationships of personality to efficient cognitive performance. These three areas of personality (introversion-extraversion, I/E; achievement motivation; and anxiety) have been shown in a number of studies to be relatively independent. Furthermore, research in all three areas has dealt with the situational and motivational determina...

An associative theory of human memory is proposed, which serves as a counterexample to claims that disassociations between episodic, semantic, and procedural memory tasks necessitate separate memory systems. The theory is based on task analyses of matching (recognition and familiarity judgments), retrieval (cued recall with list associates, extralist associates, and part-word cues), and production (producing the first word that comes to mind). These analyses are then embedded in a distributed storage model, and it is shown how proactive interference from old memories can be largely eliminated by combining cue strengths interactively at study and test. A distinction between modality-specific and more central, modality independent, memory codes is also introduced. The model is extended to the performance of amnesic patients, and the general approach to human memory is then evaluated.The theory developed in this article grew out of several theoretical dilemmas posed by the memory literature; it is an attempt to resolve them. The first dilemma concerns the nature of episodic memories: Are they uniquely encoded, as Tulving has proposed (Flexser

SUMMARYThe personality dimension of introversion/extraversion is one of the few personality dimensions that can be reliably identified from study to study and investĝ ator to investigator. The importance of this dimension within personality theory is due both to the stability of the trait and the influential theory of H. J. Eysenck. The basic assumption in Eysenck's theory of introversion/extraversion is that the personality differences between introverts and extraverts reflect some basic difference in the resting level of cortical arousal or activation. Assuming that there is a curvilinear relationship (an inverted U) between levels of stress and performance leads to a test of this arousal theory. That is, moderate increases in stress should hinder the performance of introverts who are presumably already highly aroused. However, the same moderate increase in stress might help the performance of the presumably underaroused extraverts.Revelle, Amaral, and Turriff .reported that the administration of moderate doses of caffeine hindered the performance of introverts and helped the performance of extraverts on a cognitive task-similar to the verbal test of the Graduate Record Examination. Assuming that caffeine increases arousal, this interaction between introversion/extraversion and drug condition supports Eysenck's theory. This interaction was explored in a series of experiments designed to replicate, extend, and test the generality of the original finding. The interaction between personality and drug condition was replicated and extended to additional cognitive performance tasks. However, these interactions were affected by time of day and stage of practice, and the subscales of introversion/extraversion, impulsivity, and sociability, were differentially affected. In the morning of the first day, low impulsives were hindered and high impulsives helped by caffeine. This pattern reversed in the evening of the first day, and it reversed again in the evening of Day 2.We concluded that the results from the first day of testing require a revision of Eysenck's theory. Instead of a stable difference in arousal between low and high impulsives, it appeared that these groups differed in the phase of their diurnal arousal rhythms. The result is that low impulsives are more aroused in the morning and less aroused in the evening than are the high impulsives.A variety of peripheral or strategic explanations (differences in caffeine consumption, guessing strategies, distraction, etc.) for the observed performance increments and decrements were proposed and tentatively rejected. It seems probable that some fundamental change in the efficiency with which information is processed is responsible for these performance changes. One of the few personality dimensions that most personality theorists agree is robust enough to identify from study to study and investigator to investigator is that of introversion/extraversion. It has been shown that this personality dimension can be identified in such varied item sets as behavioral measures ...