If the political conservatism of female students who join sororities is greater than that of female students who do not, the gap in the political attitudes of the two groups will probably widen as they progress through college. this would be best explained in terms of

I believe the answer is: group polarization.

group polarization refers to a situation when individual behavior become more extreme if that individual is surrounded by other group members that have a certain set of thinking. The behavior would automatically be reduced in intensity as soon as the individual moved away from the group.