Title: Deliberate Practice and the Acquisition and Maintenance of Expert Performance in Medicine and Related Domains
Abstract: The factors that cause large individual differences in professional achievement are only partially understood. Nobody becomes an outstanding professional without experience, but extensive experience does not invariably lead people to become experts. When individuals are first introduced to a professional domain after completing their education, they are often overwhelmed and rely on help from others to accomplish their responsibilities. After months or years of experience, they attain an acceptable level of proficiency and are able to work independently. Although everyone in a given domain tends to improve with experience initially, some develop faster than others and continue to improve during ensuing years. These individuals are eventually recognized as experts and masters. In contrast, most professionals reach a stable, average level of performance within a relatively short time frame and maintain this mediocre status for the rest of their careers. The nature of the individual differences that cause the large variability in attained performance is still debated. The most common explanation is that achievement in a given domain is limited by innate factors that cannot be changed through experience and training; hence, limits of attainable performance are determined by one's basic endowments, such as abilities, mental capacities, and innate talents. Educators with this widely held view of professional development have focused on identifying and selecting students who possess the necessary innate talents that would allow them to reach expert levels with adequate experience. Therefore, the best schools and professional organizations nearly always rely on extensive testing and interviews to find the most talented applicants. This general view also explains age-related declines in professional achievement in terms of the inevitable reductions in general abilities and capacities believed to result from aging. In this article, I propose an alternative framework to account for individual differences in attained professional development, as well as many aspects of age-related decline. This framework is based on the assumption that acquisition of expert performance requires engagement in deliberate practice and that continued deliberate practice is necessary for maintenance of many types of professional performance. In order to contrast this alternative framework with the traditional view, I first describe the account based on innate talent. I then provide a brief review of the evidence on deliberate practice in the acquisition of expert performance in several performance domains, including music, chess, and sports. Finally, I review evidence from the acquisition and maintenance of expert performance in medicine and examine the role of deliberate practice in this domain. The Traditional View of Skill Acquisition and Professional Development: History and Some Recent Criticisms The traditional view of skill acquisition is based on the assumption that innate biological capacities limit the level of achievement that a person can attain. Sir Francis Galton is generally recognized for developing the scientific basis for this view in the 19th century. In his pioneering book, Hereditary Genius,1 he presented evidence that height and body size was determined genetically, and most importantly, he argued that similar innate mechanisms must determine mental capacities, stating: Now, if this be the case with stature, then it will be true too as regards every other physical feature—as circumference of head, size of brain, weight of grey matter, number of brain fibres, &c.; and thence, a step on which no physiologist will hesitate, as regards mental capacity [italics added].1, pp. 31–2 At the same time, Galton clearly acknowledged the effects of practice and the need for training to reach high levels of performance in any domain. However, he argued that improvements are rapid only in the beginning of training and that subsequent increases become increasingly smaller, until “Maximal performance becomes a rigidly determinate quantity.”1, p. 15 According to Galton, the relevant heritable capacities set the upper bound for an individual's physical and mental achievements, and once all of the training benefits have been attained through sufficient practice, then the immutable limit for performance is reached that “Nature has rendered him capable of performing.”1, p. 16 According to Galton, the immutable characteristics that limit maximal performance cannot be altered through training. By extension, they must have been innately endowed. Galton's arguments for the importance of innate factors in elite performance were quite compelling and, thus, have had a lasting impact on our culture's view of ability and expertise. Contemporary theories of skill acquisition2,3 are consistent with Galton's general assumptions and with the observations on the course of professional development. When individuals are first introduced to an activity such as driving a car or playing golf, their primary goal is to reach a level of mastery that will allow them to perform everyday tasks at an acceptable level or to engage proficiently in recreational activities with their friends. During the first phase of learning,2 novices try to understand the activity and concentrate on avoiding mistakes. With more experience in the middle phase of learning, gross mistakes become increasingly rare, performance appears smoother, and learners no longer need to concentrate as hard to perform at an acceptable level. After a limited period of training and experience—frequently less than 50 hours for most recreational activities such as typing, playing tennis, and driving a car—an acceptable standard of performance is typically attained. As individuals adapt to a domain and their performance skills become automated, they are able to execute these skills smoothly and without apparent effort. As a consequence of automation, performers lose conscious control over execution of those skills, making intentional modifications difficult. Once the automated phase of learning has been attained, performance reaches a stable plateau with no further improvements, which is consistent with Galton's assumption of a performance limit. The principal difference between acquisition of everyday skills and professional development appears to be primarily a difference in time scale. Whereas proficiency in everyday skills is attained rapidly, professional development (including the prerequisite education) is completed only after years or even decades of experience. In their seminal work, Simon and Chase4 argued that in order to attain an international level of performance in chess, an individual must maintain full-time involvement in the activity for at least ten years. Their research on chess masters’ memories for regular game positions suggested that the masters had acquired some 50,000 chunks or patterns, and they highlighted the parallels between reaching this highly skilled performance level and acquiring a language with its large vocabulary. Simon and Chase4 proposed a theory of expertise where future experts gradually acquired patterns and knowledge about how to react in situations as a direct consequence of their continued experience in the domain. Based on the observation that most people are able to master their first language after many years of experience even without formal instruction, scientists started considering the possibility that sufficient experience (over ten years of full-time engagement) might automatically lead to expertise in a performance domain. Eventually, some scientists viewed sufficient length of experience in a domain (over ten years) as a reliable indicator of expertise. Several reviews over the past decade5–7 have shown that empirical evidence for the traditional views regarding the development of expertise through extended experience alone is surprisingly limited. First and most surprisingly, the performance of experts, who are nominated by their peers based on their extensive experience and reputation, is occasionally unexceptional for representative tasks from their domain of expertise. For example, highly experienced computer programmers’ performance on programming tasks is not always superior to that of computer science students,8 and physics professors from UC Berkeley were not always consistently superior to students on introductory physics problems.9 More generally, the level of training and experience has frequently been only weakly linked to objective measures of performance in a domain. For example, the length of training and professional experience of clinical psychologists is not related to their efficiency and success in treating patients,10 and extensive experience with software design is not associated with consistently superior proficiency on presented tasks.11,12 Similarly, when “wine experts” are required to detect, describe, and discriminate characteristics of a wine without knowledge of its identity (seeing the label on the bottle), their performance is only slightly better than those generated by regular wine drinkers.13,14 More generally, reviews of decision making15,16 show that experts’ decisions and financial advice on investing in stocks have surprisingly low accuracy that does not improve with additional experience. Similar phenomena have been documented in several other areas of expertise.6 In the second half of this article, I will review evidence on whether highly experienced doctors, with reputations as experts, display consistently superior performance to their less experienced colleagues and, if so, I will identify the characteristics of those medical activities that reveal such superiority. Second, the traditional views of professional development and skill acquisition assume that people will reach a stable asymptotic level of performance after sufficient experience. This assumption is inconsistent with the documented ability of highly experienced individuals to continue to improve their performance through training. Research has shown that when even highly experienced workers and professionals are appropriately motivated, they are able to improve their objective performance, sometimes dramatically.5 Finally, many efforts have been made to measure children's, adolescents', and young adults’ basic capacities, such as short-term memory and attention, as well as visual, auditory, spatial, and motor skills, to assess the possible innate limits of their attainable performance. Efforts to use these estimated capacities to predict adult professional achievement have been disappointing and largely unsuccessful.6 Efforts to identify innate individual characteristics that are critical to attaining expert performance yet are resistant to modification by extensive training have not proved fruitful.17,18 The only such innate characteristics for which the genetic difference between people and the associated mechanisms are well understood are body size and height,19,20 wherein above-average height provides an advantage in basketball, while below-average height facilitates elite performance in gymnastics. These findings raise doubts about the common-sense view of genetically determined limits that severely constrain people's attainable performance. They suggest that highly motivated individuals should be able to influence their attained performance levels to a much greater degree than is traditionally assumed. The remainder of this article addresses two broad objectives. First, emerging findings are presented on how performers attain expert levels of achievement in diverse domains, including music, sports, and chess. A particular focus here is on the role of deliberate practice and training quality in mediating improvements in current levels of performance. Second, the expert-performance approach, with its emphasis on deliberate practice, is applied to research on expertise in medicine. Here, insights gained from the study of expertise in other areas provide interesting ideas for enhancing and maintaining attained levels of performance in the medical domain. The Scientific Study of Expert Performance and Its Acquisition In the introduction to this article, several examples were given where respected experts, such as wine connoisseurs and famous stockbrokers, failed to demonstrate consistently superior performances on representative tasks, such as investing money in stocks and describing wines. Scientists can no longer assume that individuals reputed to be experts based on their extended experience will display the superior achievement indicative of expertise in a domain. Ericsson and Smith21 criticized studies of expertise that merely looked for differences between “experts” (defined by social criteria) and less experienced individuals. They proposed instead that researchers focus on superior performance in a domain and identify any individual who consistently exhibits superior performance—whether they are socially recognized as expert or not. The first step is to construct representative tasks that capture the essence of expertise in the domain where the superior performer can exhibit their superior performance in a consistent and reproducible manner. The focus on reproducible scientific evidence on superior performance provides a framework for evaluating anecdotes about the achievements of athletes, musicians, and scientists. When the “hard” scientific evidence for the most amazing achievements is scrutinized, most of these incidents cannot be substantiated by independent and unbiased sources.20 Often, the only sources of these anecdotes are the exceptional persons telling stories about their own childhood achievements when interviewed as adults. In other cases, the individuals observing the event may have misinterpreted what actually happened. For example, when a golfer sinks a 40-foot putt to win a golf tournament, it is often assumed that they did so because of their amazing ability.22 However, scientists have analyzed elite golfers’ putting accuracy at different distances during tournament conditions and conducted experiments wherein golfers are asked to make the same shot ten to 20 times in row. The results of these analyses show that the consistency of their shots is never perfect, though much higher than that of less skilled golfers.22 Even the paths of the experts’ properly played shots are influenced by random factors beyond the golfers’ control and, thus, sinking long putts is due in large part to chance factors, even for the best golfers. To build a science of exceptional performance, we need to restrict the scientific evidence to those aspects of phenomena that can be repeatedly and reliably observed, such as the expert golfers’ reduced variability in outcomes of shots. Ideally, from an empirical viewpoint, one would reproduce the everyday phenomenon of superior achievement in the laboratory, so it can be examined under standardized and experimental conditions. In many domains, it is possible to measure expert performance by observing elite performers as they reproduce their superior achievement under controlled laboratory conditions.21 Many types of superior performance by experts are reproduced repeatedly in everyday life. For example, elite runners who finish the mile in less than four minutes can reproduce their exceptional running times repeatedly at different competitions. In sports there is a long tradition of creating fair competition by designing standardized comparable conditions for all participating athletes. The same is true for competitions in music, dance, and chess. In all of these domains, elite individuals consistently outperform their less accomplished counterparts. Expert performers have trained to be able to reproduce their superior performance under representative conditions in everyday life whenever it is required during competition and training. Ericsson and Smith21 described how it is possible to identify naturally occurring activities that capture the essence of expertise in a given domain. For example, in his pioneering work on chess expertise, de Groot23 argued that the essential task for expert chess playing consists of selecting the best moves for critical positions during chess games. To study performance, de Groot extracted chess positions from games between chess masters and set up a controlled laboratory situation where he could present these positions one at a time to an individual chess player (see Figure 1). The chess players were instructed to think aloud while they selected the best move for the presented position. Ability to select the best chess moves under these conditions is closely correlated with ratings for tournament competitors.24Figure 1.: Three examples of laboratory tasks that capture the consistently superior performance of domain experts in chess, typing, and music. (From “Expertise,” by K. A. Ericsson and Andreas C. Lehmann, 1999, Encyclopedia of Creativity. Copyright by Academic Press.)Another example is found in the study of expert performance in typing. Given that expertise in typing should generalize to any kind of textual content, we can simply give all typists the same text material and ask them to type it accurately as fast as possible. The final example given in Figure 1 illustrates a common obstacle to the study of expertise, namely that experts can excel at a task that less skilled individuals are unable to complete. In the study of music expertise, for example, we are confronted with the problem that the expert musicians typically perform pieces of music that are too difficult for less accomplished musicians to master. It is, however, possible to instruct all musicians to play familiar or unfamiliar pieces of lower difficulty and then ask them to repeat their own performances in as much detail as possible. When asked to do so, experts can repeat their performances with much less deviation from their original renditions than can less skilled musicians, thus exhibiting greater control over their performance. In related approaches, snooker players can be asked to make several shots for each of a series of fixed configurations of billiard balls, and golfers can be asked to make several putts for each of many ball locations on a green.22 In sum, it is possible to identify a collection of representative tasks that capture the essence of expertise in most domains, and those tasks can be administered to all participants under controlled and standardized conditions. In the latter portion of this article, I will identify tasks that simulate the conditions for the essential activities in a few different domains in medicine, such as diagnosis and surgical treatments. The Acquisition of Superior Reproducible (Expert) Performance Having confined our attention to superior, reproducible performance that can be measured, it is possible to identify several claims about the acquisition of expertise that generalize across different domains.6,20 First, longitudinal assessments of performance reveal that performance increases gradually and that there is no evidence for abrupt increases from one trial to the next. Even when the performance of child prodigies in music and chess are measured by adult standards, the increases in achievement are found to be gradual and extended over many years. Second, the age at which experts typically reach their peak career performance is the middle to late 20s for many vigorous sports, and one or two decades later (i.e., in the 30s and 40s) for less physically intense games, as well as the arts and sciences. This continued, often extended, development beyond age 18 implies that the best individuals are able to engage in practice activities that lead to further improvements in performance even after physical maturation is reached. Finally, all performers, including the most “gifted” or “talented,” need a minimum of approximately ten years of intense involvement before they reach an international level in sports, sciences, and the arts.4,5 Most elite performers, in fact, take considerably longer to reach that level. This ten-year rule of required engagement in domain-related activities is the most compelling evidence for the necessity of experience to attain high levels of performance. From interviews with international-level performers in several domains, Bloom and his colleagues found that elite performers are nearly always introduced to their future domains of expertise as young children in a playful manner. As soon as they reveal enjoyment for the activity and show promise compared to their local peers, they receive help both in seeking out a teacher or coach and to begin regular training. Based on these interviews, Bloom25 argued that access to superior training resources during development is necessary to reach the highest levels. The best evidence for the value of current training methods and intensive schedules of practice comes from historical comparisons.22,26 The most dramatic improvements in the level of performance over historical periods are found in sports and are associated with improved quality and quantity of practice. Contemporary elite athletes’ performance is much superior to the gold medal winners of the early Olympic Games.5 In some events where performance can be measured objectively (i.e., with times or distances), current winning performances are as much as 30–50% better.27 Such a drastic improvement indicates the superiority of contemporary training methods, beyond what could be obtained through technological advances and better equipment, such as lighter running shoes, alone. To further explore the role of practice in attaining expert levels of performance, Ralf Krampe, Clemens Tesch-Römer, and I5 tried to identify those training activities that were most closely associated with consistent improvements in performance and referred to them as deliberate practice. From a review of studies of learning and skill acquisition, we found evidence for consistent gradual improvement of performance when the following conditions were met. First, the participants were instructed to improve some aspect of performance for a well-defined task. Second, they were able to get detailed immediate feedback on their performance. Finally, they had ample opportunities to improve their performance gradually by performing the same or similar tasks repeatedly. The participants were able to keep improving their performance during extended training as long as the training sessions were limited to around an hour—a time that typical college students are able to maintain sufficient concentration to sustain active efforts to improve. These deliberate efforts to increase one's performance beyond its current level involve problem solving and finding better methods to perform the tasks. Engaging in practice activities with the primary goal of improving some aspect of performance is an integral part of deliberate practice. The importance of deliberate practice in attaining expert performance was first demonstrated in a study of expert musicians studying at a famous music academy in Berlin. Three groups of the expert musicians who differed from each other in level of attained music performance were selected. All of the expert musicians were interviewed about how they spent their daily lives and were asked to keep detailed diaries of their activities for a week. Although all expert musicians were found to spend a similar amount of time when all types of music-related activities were combined, the two best groups of expert musicians were found to spend more time in solitary practice. When the experts practiced by themselves, they concentrated on improving specific aspects of the music performance as directed by their music teachers, thus meeting the criteria for deliberate practice. The best groups of expert musicians spent around four hours every day, including weekends, in this type of solitary practice. From retrospective estimates of practice, Ericsson et al.5 calculated the number of hours of deliberate practice that the three groups of musicians, along with two reference groups, had accumulated by a given age (see Figure 2). By the age of 20, the group of the best expert musicians (along with a reference group of musicians belonging to international orchestras) had spent over 10,000 hours of practice, which is 2,500 and 5,000 hours more than the two less accomplished groups of expert musicians and 8,000 hours more than a reference group of amateur pianists of the same age.28Figure 2.: Estimated amount of time for solitary practice as a function of age for the middle-aged professional violinists (triangles), the best expert violinists (squares), the good expert violinists (empty circles), the least accomplished expert violinists (filled circles) and amateur pianists (diamonds). (From “The role of deliberate practice in the acquisition of expert performance,” by K. A. Ericsson, R. Th. Krampe, and C. Tesch-Römer, 1993, Psychological Review, 100(3), p. 379 and p. 384. Copyright 1993 by American Psychological Association. Adapted with permission.)Several studies and reviews have found a consistent association between the amount and quality of solitary activities meeting the criteria of deliberate practice and performance in chess,29 in music,28,30,31 and in different types of sports.32–34 The concept of deliberate practice also accounts for many earlier findings in other domains,6 as well as for the results of the rare longitudinal study of elite athletic performers.35 Deliberate practice has even been found to be a key factor in maintaining expert levels as performers reach older ages. Although the performance of most professionals decreases, there are a few intriguing exceptions. A sufficient amount of weekly deliberate practice has been shown to allow expert pianists in their 50s and 60s to maintain their piano performances at a comparable level to that of young experts, although the older musicians displayed normal age-related declines on standardized tests.28 Similarly, older masters in the game GO are able to maintain their performance and related skills,36 and master athletes show the key importance of continued intense physical training.19,37 The age-related decreases in performance appear to result primarily from reductions of regular deliberate practice, rather than as a direct consequence of aging per se.38 Complex Mechanisms That Mediate Expert Performance and Continued Learning The fundamental theoretical challenge is to explain how most people and professionals reach a stable performance asymptote within a limited time period, whereas the expert performers are able to keep improving their performance for years and decades. When people and professionals are first introduced to an activity, their primary goal is to reach a sufficient level of mastery that is acceptable to other people in the domain. According to the traditional theory of skill acquisition,2 people need initially to concentrate on what they are going to do in order to reduce gross mistakes, as illustrated in the lower arm of Figure 3. With more experience, their salient mistakes become increasingly rare, their performance appears smoother, and they no longer need to concentrate as hard to perform at an acceptable level. After some limited training and experience—frequently less than 50 hours for most recreational activities such as skiing, tennis, and driving a car—an acceptable standard of performance is attained without much need for effortful attention. As individuals’ behaviors are adapted to the performance demands and become increasingly automated, they lose conscious control and are no longer able to make specific intentional adjustments.Figure 3.: An illustration of the qualitative difference between the course of improvement of expert performance and of everyday activities. The goal for everyday activities is to reach as rapidly as possible a satisfactory level that is stable and “autonomous.” After individuals pass through the “cognitive” and “associative” phases, they can generated their performance virtually automatically with a minimal amount of effort (see the gray/white plateau at the bottom of the graph). In contrast, expert performers counteract automaticity by developing increasingly complex mental representations to attain higher levels of control of their performance and will therefore remain within the “cognitive” and “associative” phases. Some experts will, at some point in their career, give up their commitment to seeking excellence and thus terminate regular engagement in deliberate practice to further improve performance, which results in premature automation of their performance. (Adapted from “The scientific study of expert levels of performance: general implications for optimal learning and creativity” by K. A. Ericsson in High Ability Studies, 9, p. 90. Copyright 1998 by European Council for High Ability.)In direct contrast, expert performance continues to improve as a function of more experience, coupled with deliberate practice. The key challenge for aspiring expert performers is to avoid the arrested development associated with automaticity and to acquire cognitive skills to support their continued learning and improvement. The expert performer counteracts the tendencies toward automaticity by actively acquiring and refining cognitive mechanisms to support continued learning and improvement, as shown in the upper arm of Figure 3. The experts deliberately construct and seek out training situations in which the desired goal exceeds their current level of performance. They acquire mechanisms that are designed to increase their control and ability to monitor performance in representative situations from the domain of expertise.7,22,39 For example, a chess player acquires improved memory skil