# Parasympathetic Nervous System Functioning Moderates the Associations between Callous-Unemotional Traits and Emotion Understanding Difficulties in Late Childhood

## TL;DR

This study finds that children with high callous-unemotional traits have trouble understanding emotions, especially fear, but this is less true for those with certain nervous system activity.

## Contribution

The study reveals that parasympathetic nervous system activity moderates the relationship between callous-unemotional traits and emotion understanding in children.

## Key findings

- Higher callous-unemotional traits correlate with lower emotion understanding, especially for fear.
- Parasympathetic nervous system activity moderates this relationship, with stronger effects at average or high RSA levels.
- Children with low RSA levels show no link between callous-unemotional traits and emotion understanding.

## Abstract

Background: Callous-unemotional (CU) traits are characterized by low empathy, guilt, and prosociality, putting children at risk for lifespan antisocial behavior. Elevated CU traits have been linked separately to difficulties with emotion understanding (i.e., identifying emotional states of others) and disrupted parasympathetic nervous system (PNS) functioning. However, no study has investigated how PNS functioning and emotion understanding are jointly related to CU traits. Method: We explored associations between CU traits, emotion understanding, and PNS functioning (indexed via respiratory sinus arrhythmia [RSA]) among children aged 7–10 years old (n = 55). We also tested whether deficits in emotion understanding differ across specific emotions (i.e., fear, pain, happiness, anger). Each child’s RSA was continuously recorded while they watched a film that included emotionally evocative social interactions. To assess emotion understanding, children identified emotions replayed in 1s animations of scenes from the film. Parents reported on child CU traits, conduct problems, and demographic information. Results: Higher CU traits were related to lower emotion understanding (β = −0.43, p = 0.03). PNS activity during the film moderated this association (β = −0.47, p < 0.001), such that CU traits were associated with lower emotion understanding among children with mean (B = −0.01, t = −2.46, p = 0.02) or high (i.e., 1 SD > M; B = −0.02, t = −3.00, p < 0.001) RSA levels during the film, but not among children with low RSA levels (i.e., 1 SD < M; B = 0.00, t = −0.53, p = 0.60). Moreover, we found that the observed moderated associations are driven by deficits in fear, specifically. Conclusions: The link between poorer emotion understanding, fear understanding in particular, and CU traits was attenuated for children who demonstrated patterns of PNS functioning consistent with attentional engagement while viewing the emotion stimuli.