The purpose of this study is to describe facial, behavioral and physiologic (heart rate) reactivity of children with autism aged 3 to 6 years old, during a painful stimulation (venepuncture). Children will be videotaped before, during and after a venepuncture. Each recording will be rated with the FACS (Facial Action Coding System) and the NCCPC (Non Communicating Children's Pain Checklist).

Children with autism will be matched with children with mental retardation and children without developmental disorder. Matching will be established according the developmental age of children with autism.

Inclusion Criteria:

Group Autism:

• Child aged 3 to 6 years old
• Diagnosis of autistic disorder established according a pluridisciplinary staff (ICD-10 criteria, Vineland scales, ADOS, etc.)
• Admitted to children's neuropediatrics or genetics department for a venepuncture

Control group mental retardation:

• Child aged 3 to 6 years old .
• Diagnosis of mental retardation established according a pluridisciplinary staff (ICD-10 criteria, Vineland scales, ADOS, etc.)
• Admitted to neuropediatric or genetic department for a venepuncture

Control group without developmental disorder :

• Child aged 18 months to 5 years old.
• Admitted to pediatrics department for a venepuncture

46 children with autism spectrum disorders, 46 children with mental retardation, 46 children without developmental disorder