Education and training have a very long history. Ever since Greek civilization, there has been an important distinction made between general education and vocational training, which requires the acquisition of a high level of skill. Education, as proposed by Plato and Aristotle, discouraged specialization and focused on developing thinking skills and general knowledge. With respect to skilled manual work, primarily performed by slaves in Athens,¹ Plato proposed an early start of training and restricted engagement to a single craft.^2,3 When discussing medical expertise, Plato contrasted the routine application of medical procedures by a slave doctor to the thoughtful diagnosis and reasoning about treatment and explanation to the patient by an expert doctor.⁴ Competency among doctors was thus thought to be best assessed by examining their superior knowledge⁵ and ability to teach others.⁶ The primary additional factor to achieve competence was believed to be due to accumulated experience, and thus age was expected to be correlated with wisdom. Plato argued that the ideal doctor was one with significant experience—ideally, personal experiences of recovering from many diseases.⁷

Since Aristotle, the issues of how to evaluate and certify expertise and the tension between theoretical understanding and practical skill have remained. The level of expertise of practitioners has been monitored and credentialed by guilds and more recently by professional organizations.⁸ In the United States, students typically require a general education, such as a college education, before they can be admitted to study at professional schools. Following primarily theoretical training at professional schools, graduates are trained as apprentices to experienced practitioners until they earn the credentials to practice independently.

Consistent with the distinction between general theoretical knowledge and professional skill, early traditional models of skill and expertise^9–13 distinguish different stages of development. The first stage (novice) involves following the teachers’ instruction and applying rules and procedures step by step. With increasing experience, the student becomes more able to generate the same outcomes faster and more efficiently. After extensive experience, individuals become experts and are able to respond rapidly and intuitively. Some domains, such as driving a car, are simple and “almost all novices [beginners] can eventually reach the level we call expert.”¹¹ In other more complex domains, such as telegraphy and chess, it may take decades to reach the highest levels.^13,14 Some researchers even explicitly reject the idea that expert behavior and performance needs to be uniformly superior to less experienced individuals.¹¹ The pioneering research on expertise¹³ emphasized improvements in performance due to experience in the domain. In studies of medical doctors and nurses, it was typical to search for experts by using peer-nomination procedures among highly experienced professionals.^9,15,16

In the 1980s the definition of expertise based on accumulated knowledge, extensive professional experience, and peer nominations was becoming increasingly criticized. Numerous empirical examples were reported where “experts” with extensive experience and extended education were unable to make better decisions than their less skilled peers or even sometimes than their secretaries.¹⁷ Early studies were unable to establish superior accuracy of the peer-nominated best general physicians, when compared to a group of undistinguished physicians.^15,16 Similar findings were subsequently attained for clinical psychotherapists, where more advanced training and longer professional experience were unrelated to the quality and efficiency of treatment outcomes.¹⁸ In addition, examinations of the cognitive mechanisms that mediated the actions of individuals exhibiting consistently superior performance revealed a complex structure that could not be accounted for by a mere accumulation of experience and knowledge.¹⁹ In response to these criticisms, Ericsson and Smith¹⁹ proposed the redirection of research from studying the behavior of socially recognized experts toward the study of reproducibly superior performance in a given domain.