Animals have helped many kids with autism improve their speech and social skills, but these cases have been largely isolated. Now the first scientific study of horse therapy finds its many benefits may have to do with rhythm.

A study of 42 children with autism, six to 16 years old, found that riding and grooming horses significantly bettered behavioral symptoms. Compared with kids who had participated in nonanimal therapy, those exposed to horses showed more improvement in social skills and motor skills, rated via standard behavioral assessment surveys, according to the study published in the February issue of Research in Autism Spectrum Disorders. Psychologist Robin Gabriels of the University of Colorado Denver, who led the study, speculates that the calming, rhythmic motion of the horses played a role.

Rhythmic coordination issues underlie all the symptoms of autism, including repetitive behaviors and difficulty communicating, comments Robert Isenhower, a researcher at Rutgers University who was not involved with the study. Using drumming games, Isenhower has found that children with autism struggle more than typically developing children to keep a beat. This impairment affects unconscious social behaviors that most of us take for granted, such as pausing after questions or walking in step with others. “I think the horse might serve as a surrogate motor system for individuals with autism,” he says.