Psychological Research (2007) 71:591–597 DOI 10.1007/s00426-006-0076-0 ORIGINAL ARTICLE The eVects of time pressure on chess skill: an investigation into fast and slow processes underlying expert performance Frenk van Harreveld · Eric-Jan Wagenmakers · Han L. J. van der Maas Received: 28 November 2005 / Accepted: 3 July 2006 / Published online: 22 December 2006 © Springer-Verlag 2006 Abstract The ability to play chess is generally Introduction assumed to depend on two types of processes: slow processes such as search, and fast processes such as One of the important challenges for cognitive science is pattern recognition. It has been argued that an increase to shed light on the processes that underlie expert in time pressure during a game selectively hinders the decision making. Across a wide range of Welds such as ability to engage in slow processes. Here we study the medical decision making and engineering, it has been eVect of time pressure on expert chess performance in shown that expertise involves both slow processes order to test the hypothesis that compared to weak such as selective search and fast processes such as the players, strong players depend relatively heavily on recognition of meaningful patterns (e.g., Ericsson & fast processes. In the Wrst study we examine the perfor- Staszewski 1989). This distinction between fast and slow mance of players of various strengths at an online chess processes is very applicable to the game of chess and server, for games played under diVerent time controls. therefore research on chess is of considerable impor- In a second study we examine the eVect of time con- tance for the understanding of expert performance. trols on performance in world championship matches. Ever since the groundbreaking work of De Groot Both studies consistently show that skill diVerences (e.g., 1946, 1978), cognitive psychologists have been between players become less predictive of the game interested in the skills that distinguish strong from outcome as the time controls are tightened. This result weak chess players. Generally two types of skill are dis- indicates that slow processes are at least as important tinguished; the ability to calculate variations (search) for strong players as they are for weak players. Our and the ability to recognize and remember meaningful Wndings pose a challenge for current theorizing in the patterns on the board (pattern recognition). The early Weld of expertise and chess. work by De Groot (1946) indicated that strong players are hardly any better when it comes to search. Simi- larly, Charness (1981), Holding and Reynolds (1982), and Saariluoma (1990) have shown that experts search slightly deeper than weaker players but that they do not search wider. In other words, they calculate selected F. van Harreveld (&) · E.-J. Wagenmakers · variations somewhat deeper, but they do not calculate H. L. J. van der Maas more variations than weaker players. This relatively Department of Psychology, small eVect of skill on search has led Charness (1981) Universiteit van Amsterdam, Roetersstraat 15, 1018 WB Amsterdam, The Netherlands to conclude that at high skill levels the ability to search e-mail: [email protected] probably becomes uniform. E.-J. Wagenmakers In terms of the skills that do distinguish strong from e-mail: [email protected] weak players, De Groot (1946) found that strong play- H. L. J. van der Maas ers are much better than weaker players in their ability e-mail: [email protected] to memorize and recognize patterns of pieces on the 123 592 Psychological Research (2007) 71:591–597 board. This eVect has been replicated and extended by 5 min to complete a game, demonstrated that blitz per- Gobet and Simon (Gobet & Simon 1996, 2000; Lassiter formance and chess skill are very highly correlated. 2000). These Wndings have led psychologists to believe Moreover, time pressure attenuated skill diVerences that at a certain level expert skill in chess is predomi- among weak players, but not among strong players. nantly determined by the number of chunks a player Based on the latter Wnding, Burns concluded that skill has in his “chess vocabulary” which he can access rela- diVerences in chess are predominantly based on diVer- tively fast and eVortlessly (e.g., Simon & Chase 1973). ences in the eVectiveness of fast processes, and that this Holding (1985, 1992; see also Gobet & Simon 1998), holds particularly for strong players. However, this however, has challenged this view and has emphasized conclusion may be premature, as several alternative the importance of search. explanations exist. An important diVerence between search processes From a theoretical perspective, it is indeed plausible such as calculating variations on the one hand and pat- that time pressure reduces the contribution of slow tern recognition on the other is that the former takes processes in an absolute sense. However, in a game relatively more time. In other words, search is often between two players it is the amount of search relative labeled a slow process, while recognition is seen as a to that of the opponent that is crucial. To illustrate, fast process. Consequently, restricting the time avail- assume that a strong player calculates eight moves able to a player will have more of an eVect on the ahead under normal time controls, and his weaker (slow) search process and comparatively little on (fast) opponent calculates four moves ahead. Under time pattern recognition. Gobet and Simon (1996) have pressure, the strong player and the weak player may applied this assumption in a study where they com- only calculate, say, four and two moves ahead, respec- pared the performance of Garry Kasparov (generally tively. It is unclear which time controls are more favor- considered the strongest player of all time) under nor- able to the stronger player in this example. mal tournament circumstances to his performance When the distinction between absolute eVectiveness when Kasparov was playing a simul (i.e., playing sev- and relative impact of search processes is taken into eral players at the same time) and the time to contem- account, Burns’ theoretical claim is severely undercut. plate his moves was restricted. Gobet and Simon In a way this resembles the discussion between Gobet (1996) showed that Kasparov’s chess rating (a numeri- and Simon (1996, 2000) and Lassiter (2000) about the cal measure of skill, cf. Batchelder & Bershad 1979) increased strength of computers in blitz chess as com- drops from 2,750 to 2,646 when he has to play faster. pared to normal time controls. While Lassiter (2000) Gobet and Simon concluded that imposing a time con- argues this is likely due to the fact that the human abil- straint lowered Kasparov’s quality of play only to a ity to engage in search is more hampered by the slight extent.1 Calderwood, Klein, and Crandall (1988) increased time constraints, Gobet and Simon (2000) asked grandmasters to rate the quality of moves made reply that the human diYculty could just as well be the in fast (blitz) and slow games, played by strong and consequence of having less time for pattern recognition. weak players. Their results showed an interaction Another alternative explanation of Burns’ Wndings between skill and game type, in the sense that stricter can be found in the speciWc factors that come into play time constraints decrease the quality of play particu- during a blitz game that may cause strong players to larly for weak players. On the other hand, Chabris and beneWt from faster time controls. For example, blitz is Hearst (2003) have recently shown that even grand- associated with more stress and (perhaps conse- masters make more and bigger mistakes under condi- quently) more “blundering” (making very gross mis- tions where they have less time than usual to select takes) than normal time controls. Being less their moves. experienced, a weaker player is less used to dealing Like Gobet and Simon (1996), Burns (2004) hypoth- with stress during a game than a seasoned profes- esized that increasing time pressure selectively reduces sional—hence, the weaker player may fall victim to the eVectiveness of slow search processes. Analysis of blundering even more often than during a normal several blitz tournaments, in which a player has only game. This diVerential increase in blunders due to stress might also explain the Wnding that strong players 1 One can question whether Kasparov himself would actually con- become relatively stronger as a result of increased time sider a 100-point decrease in rating “slight.” At the time of the pressure. In short, the fact that reducing the time avail- simultaneous exhibitions he would have dropped to somewhere able leads to more variance in results among weak around tenth place. In our view, and probably in the view of the strongest player of all time, still a signiWcant decrease. At this mo- players than among strong players could be due to ment he would drop from being the strongest player in the world many factors other than the enhanced reliance of to somewhere around the 60th place in the world ranking. strong players on pattern recognition. 123 Psychological Research (2007) 71:591–597 593 A second issue is methodological. Burns used chess tionale des Echecs (FIDE) masters (FMs) and 75 play- ratings as an objective measure of chess skill, as is ers with no title. All of these players were very active indeed accepted practice. However, low ratings are on the ICC and had highly reliable ratings. estimated less reliably than high ratings. The standard On ICC there are generally two methods of Wnding deviation in the rating of amateurs is about twice that an opponent. One can directly challenge another of grandmasters (Jonker 1992). This diVerence in reli- player to a game of bullet (1–2 min), blitz (3–10 min), ability occurs because many amateurs have ratings that or standard (10–60 min).