Two large, diverse samples of tournament-rated chess players were asked to estimate the frequency and duration of their engagement in a variety of chess-related activities. Variables representing accumulated time spent on serious study alone, tournament play, and formal instruction were all significant bivariate correlates of chess skill as measured by tournament performance ratings. Multivariate regression analyses revealed that among the activities measured, serious study alone was the strongest predictor of chess skill in both samples, and that a combination of various chessrelated activities accounted for about 40% of the variance in chess skill ratings. However, the relevance of tournament play and formal instruction to skill varied as a function of skill measurement time (peak vs. current) and age group (above vs. below 40 years). Chess players at the highest skill level (i.e. grandmasters) expended about 5000 hours on serious study alone during their first decade of serious chess play-nearly five times the average amount reported by intermediate-level players. These results provide further evidence to support the argument that deliberate practice plays a critical role in the acquisition of chess expertise, and may be useful in addressing pedagogical issues concerning the optimal allocation of time to different chess learning activities.

Applied psychologists have long been interested in examining expert performance in complex cognitive domains. In the present article, we report the results from a study of expert cognitive skill in which elements from two historically distinct research paradigms are incorporated -- the individual differences tradition and the expert-performance approach. Forty tournament-rated SCRABBLE players (20 elite, 20 average) and 40 unrated novice players completed a battery of domain-representative laboratory tasks and standardized verbal ability tests. The analyses revealed that elite- and average-level rated players only significantly differed from each other on tasks representative of SCRABBLE performance. Furthermore, domain-relevant practice mediated the effects of SCRABBLE tournament ratings on representative task performance, suggesting that SCRABBLE players can acquire some of the knowledge necessary for success at the highest levels of competition by engaging in activities deliberately designed to maximize adaptation to SCRABBLE-specific task constraints. We discuss the potential importance of our results in the context of continuing efforts to capture and explain superior performance across intellectual domains.

Objectives-The goal of this article is to identify some of the major trends and findings in expertise research and their connections to human factors.Background-Progress in the study of superior human performance has come from improved methods of measuring expertise and the development of better tools for revealing the mechanisms that support expert performance, such as protocol analysis and eye tracking.

In two studies, the SCRABBLE skill of male and female participants at the National SCRABBLE Championship was analyzed and revealed superior performance for males. By collecting increasingly detailed information about the participants' engagement in practice-related activities, we found that over half of the variance in SCRABBLE performance was accounted for by measures of starting ages and the amount of different types of practice activities. Males and females did not differ significantly in the benefits to their performance derived from engagement in SCRABBLE-specific practice alone (purposeful practice). However, gender differences in performance were fully mediated by lower engagement in purposeful practice by females and by their rated preference for playing games of SCRABBLE-an activity where more extended engagement is not associated with increased SCRABBLE performance. General implications from our account of gender differences in skill acquisition are discussed, and future research is proposed for how the duration of engagement in effective deliberate practice can be experimentally manipulated.

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