Empathy refers to one’s sensitivity to others’ mental state. It is an essential ability in social interaction and is conducive to individual survival. As a subgroup of empathy, empathy for pain refers to one’s empathy for the person in pain. In previous studies, empathy for pain in humans is usually assessed by well-validated questionnaires, behavioral paradigms, and brain activity recordings, whereas empathy for pain in animals is typically measured by modulation of pain sensitivity. The underlying premise of the measurement strategy for animal empathy is that pain sensitivity is highly correlated with empathy for pain. Although some behavioral and neuroimaging studies have supported the covariant relationship between pain sensitivity and empathy for pain, it is still unclear how pain sensitivity and empathy for pain are related. The purpose of this study was to investigate the detailed relationship between pain sensitivity and empathy for pain and its influence factors in healthy participants through three interrelated experiments.
Experiment 1 investigated the relationship between individual pain sensitivity and trait empathy, as well as the role of pain-related psychological factors in this relationship. One hundred and ninety-six participants completed questionnaires developed to assess trait empathy, pain-related anxiety, depression, pain catastrophizing, and pain-related fear, and performed a cold pressor test that assesses pain sensitivity by pain threshold and pain tolerance. The results showed that pain sensitivity was positively correlated with empathic concern and personal distress scores; the relationship between pain sensitivity and emotional empathy was mediated by pain-related anxiety, pain catastrophizing, and pain-related fear. These findings suggest that individuals with higher pain sensitivity have stronger emotional empathy, and pain-related anxiety, pain catastrophizing, and pain-related fear play a mediating role in it.
Experiment 2 examined the relationship between individual pain sensitivity and state empathy for pain, as well as the role of pain-related psychological factors in this relationship. Fifty participants completed pain-related questionnaires, the cold pressor test, and an empathy for pain task with their brain activity recorded by electroencephalography (EEG). Participants’ empathy for pain was quantified via differences in subjective ratings and event-related potentials (ERPs) amplitudes between painful and non-painful conditions in the empathy for pain task. The results showed that pain sensitivity was positively correlated with pain intensity ratings, unpleasantness ratings, and amplitudes of empathic P3 component and the late positive potential; the relationship between pain sensitivity and empathic ERP responses was mediated by pain-related fear. These findings suggest that individuals with higher pain sensitivity have stronger empathy for pain, and pain-related fear plays a mediating role in it.
Experiment 3 explored the effect of empathy for pain on self-pain perception and examined whether the effect is modality-specific. Thirty-eight participants completed an EEG experiment in which painful or non-painful pictures were presented as prime stimuli, and painful or auditory stimuli were delivered as target stimuli. Participants were required to rate the intensity, unpleasantness, and salience of the target stimulus. The behavioral results showed that empathy for pain increased intensity ratings of high-intensity and low-intensity painful stimuli, as well as high-intensity auditory stimuli, while its effect on intensity ratings of low-intensity auditory stimuli was not significant. Besides, empathy for pain increased unpleasantness and salience ratings of high-intensity and low-intensity stimuli. The EEG results showed that while empathy for pain exaggerated the amplitude of laser-evoked N2 component, it had no significant effect on the amplitudes of auditory-related N2 and P2 components as well as laser-evoked N1 and P2 components. These findings suggest that empathy for pain has enhancement effects on both subsequent pain and auditory perception, and the enhancement effect on pain perception is specific to some extent.
This study systematically investigated the relationship between pain sensitivity and empathy for pain and its influence factors at both behavioral and electrophysiological levels. Healthy individuals with higher pain sensitivity show stronger empathy for pain, which can be explained by the involvement of similar psychological representations in the processing of self-pain and others’ pain. These representations are, to a certain extent, specific to the pain modality. These findings reveal the psychological connections between pain sensitivity and empathy for pain, support the shared-representation model of empathy, and provide important insights into using pain sensitivity to quantify empathy for pain.