Visual span in expert chess players: evidence from eye movements

The reported research extends classic findings that after briefly viewing structured, but not random, chess positions, chess masters reproduce these positions much more accurately than less- skilled players. Using a combination of the gaze-contingent window paradigm and thechange blindness flicker paradigm, we documented dramatically larger visual spans for experts while processing struc- tured, but not random, chess positions. In addition, in a check- detection task, a minimized 3 ◊ 3 chessboard containing a King and potentially checking pieces was displayed. In this task, experts made fewer fixations per trial than less-skilled players, and had a greater proportion of fixations between individual pieces, rather than on pieces. Our results provide strong evidence for a perceptual encoding advantage for experts attributable to chess experience, rather than to a general perceptual or memory superiority. Simon and Chase (1973) proposed that much as Drosophila can be used as a model organism for the study of genetics, chess offers cognitive scientists an ideal task environment for the study of skilled performance. Since 1946, when de Groot (1978) conducted his pio- neering investigation showing that perception and memory are more important differentiators of expertise than is the ability to think ahead in the search for good moves, chess research has been instrumental in enhancing understanding of human expertise (Ericsson & Charness, 1994) and in contributing to the study of artificial intelligence (Char- ness, 1992). In a classic study, Chase and Simon (1973a, 1973b) replicated and extended de Groot's findings that after viewing chess positions for only a few seconds, chess masters were able to reproduce these positions much more accurately than less-skilled players. There was little difference in performance as a function of expertise when random board configurations were used, indicating that the superior immediate memory performance of the skilled players was not attrib- utable to a general superiority or unique structure of their memory systems or processes (e.g., photographic memory; see Binet, 1894). Rather, Chase and Simon postulated that experts use chess knowledge to create meaningful chunks consisting of several chess pieces, and are thus able to encode structured, but not random, chess configura- tions more quickly and accurately. More recently, a very small but reliable advantage in recall for random configurations has been shown for more expert players, though this is probably attributable to the occasional presence of familiar chunks in random positions (Gobet & Simon, 1996a). Further illustrating the critical importance of knowl- edge structures for performance, Chi's (1978) work comparing chil- dren who were skilled chess players with novice adults showed an advantage for children in chess recall, but an advantage for adults in digit recall. Chase and Simon (1973a, 1973b) hypothesized that much of the skilled chess player's advantage lies in the early perceptual organiza- tion and internal representation of the chess position. Specifically, they argued that the link between skilled perception and skilled prob- lem solving was to be found in the associations between perceptual chunks and generation of plausible moves. The size of an expert's vocabulary of chess-related configurations was initially estimated to be 50,000 to 100,000 chunks (Simon & Gilmartin, 1973), although small perceptual chunks are most likely supplemented by larger struc- tures termed templates (Gobet & Simon, 1996b).