[jiaweihli]

You're describing a fixed vs. growth mindset. This applies both to your current perception of people (notably children), and also your perception of yourself when you're a child.

I believe in the growth mindset - to explain your example of sibling dominance, I believe that a child's mindset heavily influences their ability to learn. If it has a positive effect, the preparation they do is both more effective and more bountiful (this is usually classified as stubbornness / determination). But preparation _is_ necessary to perform a task at a high level. When you hear of 'prodigies', they often started whatever it was - math, music, sports, programming - at a very early age, and reaped the interest.

[blahblah3]

Why not both? Both preparation and inherent ability are important. I find it implausible that everything can be explained by "mindset." Perfect pitch is a good example, it's a useful ability and cannot really be developed through training. Other factors are more subtle but are also fixed.