What distinguishes a few exceptional talents from a mediocre majority? Is it hours upon hours of monotonous dedication to perfecting a skill? Or is it rather an innate gift, like a natural ability or talent?

The nature versus nurture debate as applied to intelligence and expertise is not new. Since the mid-1800s scientists have been questioning whether experts are “born” or “made”. Sir Francis Galton, the 19th-century founder of the field of behavioral genetics, proposed that experts are born to be experts. He believed that ultimately our innate abilities limit the level of performance an individual can achieve, and practice is only necessary for reaching an expert level of performance. Yet later mid-20th century psychologists - like John Watson, one of the founders of behaviourism - denied innate abilities or the existence of talent, and instead proposed that practicing more intensively than others is probably the only reasonable explanation for success and accomplishment.

An alternative theory, called ‘deliberate practice’, has become more popular in recent years thanks to Malcolm Gladwell's popular book, Outliers. It suggests that an accumulated amount of practice reflects expert performance. In other words, the more you practice, the better you become. Gladwell also popularised the “10,000-hour rule”- that is, the suggestion that practicing any skill for 10,000 hours is sufficient to make you an expert.

However, a new study published in Psychological Science suggests otherwise. A team of sceptical psychologists has challenged the fashionable deliberate practice theory by testing whether it's supported by experimental evidence. The results make it clear that 10,000 hours of practice is not a guarantee of expertise in every field.

The researchers from Princeton University, led by psychologist Brooke Macnamara, conducted a meta-analysis of the available scientific literature on deliberate practice in music, sports, educations, games and professions. A meta-analysis is a kind of "study of studies", where scientists try to look at the big picture in a field and reconcile the findings of multiple studies from different teams around the world. While the implications of a single study on deliberate practice might be only mildly useful, when statistically analysed with similar research it can give results that are much more definitive. Meta-analyses have been vital in proving that there is no link between vaccines and autism, for example.

The results showed that 26 per cent of the variance in individual performance for games could be explained by practice, dropping to 21 per cent for music and 18 per cent for sports. Interestingly, deliberate practice was shown to be far less important for education - a minuscule 4 per cent - and less than 1 per cent for professions (the study doesn't define what this is, but it appears to be business skills). [UPDATE: Thanks to Andy Fugard/@inductivestep for tweeting that there is a definition of "professions" hidden in the study's supporting materials - it's a category that includes four papers, on programming, football refereeing, insurance agents and pilot skills.]

Therefore, the findings confirmed the researchers' suspicions, demonstrating that overall, individual differences in expertise, skill or performance, was not considerably affected by the amount of practice accumulated over time. With individual practice explaining 26 per cent, 21 per cent and 18 per cent of the variance for some domains, it is important to note that it is not completely useless for domains such as games, music and sports. However, for the education and professional domains, practice seemed to have significantly less of an impact, begging the question - if practice doesn’t matter so much, what does?

The researchers concluded that more influential factors could perhaps include the age at which a person becomes involved in an activity, or cognitive abilities such as working memory. Perhaps it isn't that "practice makes perfect", but that "practice plus other factors makes perfect".