McMillan, F. D. 2016. The psychobiology of social pain: Evidence for a neurocognitive overlap with physical pain and welfare implications for social animals with special attention to the domestic dog (Canis familiaris). Physiology & Behavior 167, 154-171.

Social pain is the negative affect signaling threat or harm to social relationships. Loneliness is perceived social isolation and can be found across phylogeny. Evidence from diverse fields demonstrates an overlap of social and physical pain. Social pain can elicit extreme distress, which may exceed that of physical pain. Social pain has major implications for the welfare of social animals, notably dogs.