I (Lori) once had a father come in for testing for his 5-year-old son. The father noticed sensory differences with his son (e.g., overreaction to noises, sensitivity to touch, clothing), so he had taken him to an occupational therapist for testing and treatment. After a few months, he was making some progress, but his kindergarten teacher was still very concerned about his behavior. His father was then referred to me, a psychologist, for more testing to look into ADHD. When I first met with the father, he expressed the typical ADHD concerns: his son had difficulty paying attention, was very distractible, disrupted the learning of other children, and was constantly moving and talking. He was completing little work at school due to his lack of focus.

However, there were also other concerns which were characteristics of autism. For instance, he had never really made friends with anyone and was often fighting with other children at recess. He liked to spend a lot of time at home lining up...