2 methodological issues: >> They interviewed three groups of 13 violinists [...] before having them complete daily diaries of their activities over a week. Yo

2 methodological issues: >> They interviewed three groups of 13 violinists [...] before having them complete daily diaries of their activities over a week. You're basically priming interviewees, and without a control group, you're unable to partial out the variance due to "being interviewed". They need diaries from people who were interviewed _after_ taking diaries, and a group of people never interviewed. >> [... ] complete daily diaries of their activities _over_a _week. While the less skilful violinists clocked up an average of about 6,000 hours of practice by the age of 20, there was little to separate the good from the best musicians, with each logging an average of about 11,000 hours Extrapolation from a 1-week diary to your entire life until age 20?