Autism can take some time to diagnose. An autistic child's parents are usually the first to notice something different about their son or daughter. They may notice that their child behaves differently from other children the same age, for example, in the way he or she communicates with others. When unusual behavior continues, parents often consult a doctor. This is the beginning of a complex process of diagnosis. There are no medical tests for autism, and a child with autism very often has normal physical tests; consequently, it may take months or even years to diagnose the disorder. If autism is suspected, both the parents and the doctors begin a period of observation. Over time, through the use of interviews, questionnaires, and consultations with specialists, it may be determined that the child has autism.