The whiny kids tended to grow up conservative, and turned into rigid young adults who hewed closely to traditional gender roles and were uncomfortable with ambiguity. The confident kids turned out liberal and were still hanging loose, turning into bright, non-conforming adults with wide interests. The girls were still outgoing, but the young men tended to turn a little introspective.
Despite some criticisms of the study, Slate had this to add:
This matches a 2003 analysis that suggested "people who are dogmatic, fearful, [and] intolerant of ambiguity ... are more likely to gravitate to conservatism."