Vagal Tone and the Spontaneous Facial Expressions of Preschool Children.

Vagal tone, a measure of the neural modulation of heart rate, has been associated with greater emotional expressiveness during infancy, but with a decrease in facial expressivity in preschool children. This study examined the relationship between vagal tone and the emotion regulation abilities of preschool girls and boys. The study population included 25 girls and 29 boys with a mean age of 67 months. Three minutes of resting cardiac activity was obtained while children listened to an emotionally neutral story, and vagal tone was computed from a measure of cardiac interbeat interval. Spontaneous facial expressions were recorded as the children watched a set of emotion-eliciting films. In general, children with high vagal tone displayed fewer facial expressions while watching the films than children with low vagal tone. Children with high vagal tone exhibited fewer happy expressions and fear expressions than children with low vagal tone. Gender differences were also identified. Girls were more facially expressive and tended to show more fear expressions than boys. Girls with high vagal tone displayed fewer anger facial expressions than girls with low vagal tone, while boys with high vagal tone exhibited somewhat more anger expressions than boys with low vagal tone. Results support the hypothesized relationship between vagal tone and emotion regulation abilities. (AC)