Daylia,

most probably Donuel has misrepresented or misunderstood what he has read. What he actually writes re twins makes not much sense. What he probably meant to write was the following:

If one twin is a social psychopath the probability that the other is a social psychopath as well is higher than 4 %, even more so for identical twins. (That would make sense if genetic factors play a role beside other factors).

Wolfgang