> Since the out group will exclude people with both traits there should also be a negative correlation there Not necessarily. Imagine the traits are distribute

> Since the out group will exclude people with both traits there should also be a negative correlation there Not necessarily. Imagine the traits are distributed uniformly and independently in [-1 1]. There is no correlation: ****** ****** ****** ****** ****** ****** If you select people with at least one positive trait you will find negative correlation in the group + but the correlation will still be zero in the group -. ++++++ ++++++ ++++++ ---+++ ---+++ ---+++