Nisbett is wrong,I have an IQ over 150, the doctors could never agree on a number and didn't even understand there own test. I was 10 at the time. You are born with it and can not increase it. Look at it like a empty container, some can hold a quart others a gallon but it is what it is. It is simply a potential capacity at it's fullest and not predictor of future achievement. The kid could end up a janitor or teacher know one knows.

Well one must not go into whether Nisbett is wrong or right. Intelligence is a vast thing. Mozart wouldnt be able to do quantum physics and Einstien wouldnt be able to create music like Mozart. But both of them are obviously extremely intelligent. Hence Intelligence has been grouped into various kinds of intelligences. It is not possible for a single IQ test to gauge every possible kind of intelligence. Hence IQ tests gauge general factors like data assimilation, cognition, speed, deduction capacities etc. This testing is obviously age group based. Pranav obviously displayed these qualities at a very high level. These abilities at a young age are more genetic. Later on as the child grows up his/her intelligence might increase, stay static or decrease with respect to his/her age group based on nurturing from various entities.
However, the piont of contention here is the score. There are various ways of scoring an IQ test and there is no accepted generalized rule. Thus saying that the child has 176 score and Einstien has 160 is unscientific since Einstien may not have taken the same test, he does not belong to the same age group and Pranav's IQ test may have a different scoring rule. Thus one must not compare using the score figure.
However, scoring 176 in his IQ test definitely displays tremendous potential and is most definitely genetic especially since he is only 6 years old.