EMBODIED RESPONSES TO OTHERS’ PAIN: BRAIN–BODY SIGNATURES IN RATS AND HUMANS

If someone breaks a leg in front of you, how do you feel? Many people report an immediate visceral response—a racing heart, a held breath, or a sudden muscle tension. Though uninjured, the body reacts as if affected. This illustrates how social information processed by the brain can directly engage bodily responses. While social neuroscience has largely focused on brain circuits involved in such responses, how these experiences are embodied remains less well understood.

Here, we examined bodily responses to pain observation using a cross-species approach in rats and humans. Observers witnessed another individual receiving mild footshocks, allowing direct comparison of behavioral and physiological responses. We quantified global behavior and motion together with muscle tone (EMG), respiration, cardiac activity, and pupil size as markers of motor and autonomic engagement.

Across species, pain observation elicited clear and decodable bodily signatures, with high classification accuracy, especially for muscle tone and motion. In rats, responses showed a rapid global arousal followed by immobility characterized by a slower cardiac downregulation; this immobility displayed features distinct from that observed during sound-evoked fear conditioning. In humans, similar response patterns were present but markedly attenuated.

Together, these results reveal conserved embodied signatures of social pain across species and help clarify how bodily states contribute to the emotional dynamics underlying empathy.