devoting a large amount of time to learning about a field and practicing and applying that learning, have become acknowledged as being extremely knowledgeable or skilled in the particular field. For example, by spending 10,000–20,000 hours playing and studying chess, some chess players have reached the rank of grand master (Chase & Simon, 1973a, 1973b). Not surprisingly, experts tend to be better than nonexperts at solving problems in their field. Research on the nature of expertise has focused on determining differences between the way experts and nonexperts go about solving problems.