otherwise ordinary child?

[bosunyum]

This is about a prodigy and i am not sure what does the underlying part means. can you explain what it mean?

1.Son's parents are at a loss to explain why their otherwise ordinary child is a whiz at the ancient board game.

2. To him, the nuance-filled strategies and logic of chess play is something that comes as naturally as chewing bubble gum.
what kind of stragies is nuance filled strategies?

3. But bigger incomes and the rise of an ambitious middle class have produced a boom in accomplished youngsters.
what does the underlines part mean? does it mean smart children could acive success because of their parents? or what else?

4. O’Boyle believes prodigies also can switch very efficiently between the brain’s left and right hemispheres, utilizing other mental resources and perhaps even shutting down areas that produce random distractions.
this sentence is really confusing for me to understand, especailly the underlined part. Is it possible for you to paraphrase this sentnece for mean?
Thanks in advance and I am looking forward to seeing your reply.

[Tdol]

1- The child is ordinary in all other ways
2 The differences between the strategies are very subtle
3 There has been a large increase in thenumbers of talented youngsters
4 mental resources= parts of the brain they can use, shutting down refers to those areas of the brain that are not relevant to the task