Cardiac arrhythmia and behaviour in autistic children.

The behavior and heart rate of autistic children were simultaneously videorecorded in a standard situation. Normal children of two age-groups were also studied. It was found that the heart rate of the autists was characteristically highly variable and more so than that of normal children of the same age or younger. This variability (arrhythmia) however, was behaviour-dependent in all children-involvement in a task resulting in suppresion of the arrhythmia. It was at a maximum in the autists during the performance of stereotyped behaviours. The functional implications of these behaviour-heart rate associations are discussed.