A multimethod assessment of anxiety and problem behavior in children with autism spectrum disorders and intellectual disability.

Tassé et al. (2013) watched kids with autism and intellectual disability during two tasks. One task made the kids nervous. The other stayed calm.

The team used three tools at once. They counted problem behavior. They taped heart rate. They tracked breathing-linked heart rhythm called RSA.

Each child served as his own control. The single-case design let the team compare high-anxiety moments with low-anxiety moments for the same kid.

When anxiety went up, problem behavior doubled. Heart rate also jumped. RSA dipped, showing the body’s calm system was shutting off.

The same child looked different across conditions. The trio of signals moved together every time. This pattern told the team anxiety was driving the behavior, not just tagging along.

Rzepecka et al. (2011) surveyed parents two years earlier. Sleep plus anxiety explained almost half of challenging behavior in the same dual-diagnosis group. Tassé et al. (2013) added live physiology to back up that survey link.

Varela et al. (2023) later compared parent anxiety forms with saliva cortisol. Parent scores and cortisol did not match. The 2013 heart-rate data now give you a second, on-the-spot check when you doubt parent report.

Palka Bayard de Volo et al. (2021) took the same heart-rate idea into treatment. They paired watches with FCT for preschoolers. Problem outbursts shrank while heart rate fell, showing the 2013 assessment method can guide real interventions.

You now have a quick, low-cost way to test if anxiety fuels problem behavior. Tape a small heart-rate sensor, note RSA on free phone apps, and watch behavior for five minutes. If all three rise together, write anxiety into your FBA. Build calming breaks, not just escape extinction, into the plan.