Which characteristic was found to be the least closely correlated in studies of identical twins reared together versus identical twins reared apart?

Identical twins are "monozygotic" which means they developed from a single fertilized egg that split. The likelihood of identical twins is about 3 in 1,000, almost the same Identical twins reared apart constitute two individuals with the same genotype (genetic constitution) reared in two different environments. The study of a series of such twins reared apart and reared together showed that influence of genetic and environmental factors on measured characteristics (phenotypes) of the twins is the least closely correlated.