[1] Univ London, Birkbeck Coll, Ctr Brain & Cognit Dev, London WC1E 7HX, England
[2] McGill Univ, Dept Psychiat, Montreal, PQ H3A 1A1, Canada
[3] La Trobe Univ, Sch Psychol Sci, Olga Tennison Autism Res Ctr, Bundoora, Vic 3086, Australia
[4] Univ London, Ctr Res Autism & Educ, Inst Educ, London WC1H 0AL, England
[5] Kings Coll London, Inst Psychiat, London SE5 8AF, England
[6] Univ Cambridge, Autism Res Ctr, Cambridge CB2 8AH, England