An inverted U-shaped relationship between heart rate deceleration and empathic emotions.

Previous studies have shown that the high frequency component of heart rate variability is associated with empathic emotions (empathic concern and personal distress) negatively and quadratically-there is an inverted U-shaped relationship between tonic parasympathetic nervous system (PNS) activity and empathy. However, it is unclear whether the inverted U-shape also applies to the relationship between phasic PNS activity and empathic emotions. Therefore, the present study addressed this issue. Participants were asked to empathize with others' negative states (and neutral states as the control condition), followed by evaluating their own emotions. We measured the participants' cardiac activity during this task by electrocardiogram. Results revealed an inverted U-shaped relationship between heart rate deceleration, which reflects phasic PNS activity, and subjective personal distress and empathic concern. These results suggest that moderate levels of phasic PNS activity are more strongly associated with personal distress and empathic concern than low or high levels of PNS activity.