The main result of De Groot's ( 1978) classical study of chessplayers' thinking was that players of various levels of skill do not differ in the macrostructure of their thought process (in particular with respect ot the depth of search and to the number of nodes investigated). Recently, Holding (1985), 1992) challenged these results and proposed that there are skill differences in the way players explore the problem space. The present study replicates De Groot's (1978) problem solving experiment. Results show that Masters differ from weak players in more ways than found in the original study. Some of the differences support search models of chess thinking, and other pattern recognition models. The theoretical discussion suggests that the usual distinction between search and pattern recognition models of chess thinking is unwarranted, and proposes a way of reconciling the two approaches.
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