Not sure it is all about practicing. I have been a frustrated musician for years and practice more than most. I will never reach the level of mastery someone with innate talent has. I do agree with your premise that we overvalue IQ tests, they are not an indicator of anything more than potential in academics. I have had students who were special education students with low IQs who with hard work and determination could overcome challenges and do well in class while "smart kids" barely got by. In the end I think it is a combination of potential and hard work, 80% being hard work. Great article.