1. University of Cambridge, Departments of Experimental Psychology and Psychiatry, Downing Street, Cambridge CB2 3EB
2. Newcomen Centre, UMDS, Guy's Hospital, London SE1 9RT
3. Behavioural Sciences Unit, Institute of Child Health, London WC1N 1EH
4. Department of Human Communication and Science, University College London, London WC1N 1PG, UK
5. Delaware Autistic Program, 144 Brennan Drive, Newark DE 19713, USA