Original sentence: Most arguments around IQ center on the issue of correlation -- the claim that the test measures an actual thing requires that the answers to various questions will correlate highly; the claim that this thing is inherited requires that the scores of respondents who are closely related will correlate significantly more highly than results of those distantly related.Most of Gould's criticisms pertain to cases where the data seems to be legitimate.One thing he points out is that much of the data that earlier scientists relied on may have been falsified.Serious questions have been raised as to the actual extent of Burt's research (but recent studies have yielded reliable estimates of the heritability of intelligence, which fall within the same quantitative range as Burt's figures).The prime example is Cyril Burt's famous study of the IQs of twins separated at birth.This is why studies of twins separated at birth, and of adopted children, are given so much attention
Edited sentence: Most arguments around IQ center on the issue of correlation -- the very claim that the test measures an actual thing requires that the kinds of answers to various questions will correlate highly; the claim that this thing is inherited requires that the scores of respondents who are closely related will correlate significantly higher than results of those distantly related.Most of his criticisms pertain to cases where the data seems to be legitimate.One thing he points out is that much of the data used by earlier scientists was falsified (for example, in the case of a famous study of the IQs of twins separated at birth)