This article on memory and the minds of experts is intriguing for a number of reasons, and I encourage you to check out the full article here. However, the bit I found most relevant is as follows:

“Thus, motivation appears to be a more important factor than innate ability in the development of expertise.”
– Phillip E. Ross

Of course, there’s a motivation for any person to want to believe that expertise (and Ross is referring to performance, not just “knowledge”) is related to effort and I recommend a healthy dose of cynicism when people come up with conclusions which are in their best interest.