Piloting a battery to evaluate parasympathetic reactivity and externalizing behaviours during early childhood in autism spectrum disorder

Respiratory Sinus Arrhythmia Reactivity (RSA‐R) correlates both positively and negatively with externalizing behaviour in autistic individuals. These inconsistencies may result from task‐based differences. This pilot study measured RSA‐R in 4‐to 6‐year‐olds, across two timepoints, using four validated tasks with matched baseline and challenge periods. Social, cognitive, sensory and emotional tasks were employed to evaluate the use of a domain‐specific approach in measuring RSA‐R in young autistic children. RSA and parent‐reported externalizing behaviour were collected from 16 children (Mage = 5.60 years; 13 male; 12 White/Caucasian; 15 non‐Hispanic/Latine). RSA‐R was measured by the difference score of the challenge task minus its corresponding comparison task. Correlations were computed to evaluate associations between RSA‐R and behaviour. RSA was reliably measured for 3/4 tasks (0.694 ≤ intraclass correlation coefficients [ICCs] ≤ 0.896). Only RSA‐R during a social task correlated with externalizing behaviour. These results support using a battery that measures a range of challenges, differing in social demands, to characterize how arousal contributes to emotion regulation demands among young autistic children.