[1] Univ Colorado, Inst Behav Genet, Boulder, CO 80309 USA
[2] Vrije Univ Amsterdam, Dept Biol Psychol, Amsterdam, Netherlands
[3] Kings Coll London, SGDP Ctr, Inst Psychiat, London WC2R 2LS, England
[4] Queensland Inst Med Res, Brisbane, Qld 4006, Australia
[5] Univ Minnesota, Dept Psychol, Minneapolis, MN 55455 USA
[6] Ohio State Univ, Dept Human Dev & Family Sci, Columbus, OH 43210 USA