While there is no one behavioral or communications test that can detect autism, several screening instruments have been developed that are now being used in diagnosing autism:
- CARS rating system (Childhood Autism Rating Scale), developed by Eric Schopler in the early 1970s, is based on observed behavior. Using a 15-point scale, professionals evaluate a child's relationship to people, body use, adaptation to change, listening response, and verbal communication.
- The Checklist for Autism in Toddlers (CHAT) is used to screen for autism at 18 months of age. It was developed by Simon Baron-Cohen in the early 1990s to see if autism could be detected in children as young as 18 months. The screening tool uses a short questionnaire with two sections: one prepared by the parents; the other by the child's family doctor or pediatrician.
- The Autism Screening Questionnaire is a 40-item screening scale that has been used with children age four and older to help evaluate communication skills and social functioning.
- The Screening Test for Autism in Two-Year Olds is being developed by Wendy Stone at Vanderbilt and uses direct observations to study behavioral features in children under two. She has identified three skill areas that seem to indicate autism: play, motor imitation, and joint attention.