Effects of Mounted vs Unmounted Human-Equine Interaction on Autistic Youth

The goal of this clinical trial is to learn how interacting with horses affects autistic children and youth. The main questions it aims to answer are: * How does interacting with horses affect cortisol, heart-rate variability, and electrodermal activity in autistic children and youth? * How does interacting with horses affect parent-reported behaviors in autistic children and youth? Researchers will compare riding a horse, brushing a horse, and brushing a pretend stuffed horse to see if there are different effects on autistic children's physiology and behavior. Participants will * Attend three different horsemanship lessons on three consecutive weeks. One horsemanship lesson will be mounted (riding), one unmounted (brushing), and one with a pretend horse (brushing). * Wear monitors on their chest and wrist * Provide saliva samples

Inclusion Criteria: * ages 6-16 years old * met the clinical cut-offs for autism on the Autism Diagnostic Observation Schedule Second Edition and Social Communication Questionnaire * had a nonverbal IQ \>40 using the Leiter-3 (CITE) * scored \>10 on the Aberrant Behavior Checklist (CITE) Irritability Scale * could participate in study procedures (ride and groom a horse, provide saliva sample, don monitors). In addition, to be included, parents/guardians were required to live with their child at least fifty percent of the time, complete the questionaries in English, and attend all sessions with their child. Exclusion Criteria: * ridden a horse for ≥10 hours in the past six months * weighed \>200 lbs. per riding center policy * smoked or were currently using steroids due to their effects on cortisol * or if a sibling was already enrolled in the study