In biology and behavioural psychology, social defeat refers to the physiological and behavioral effects on the losing party in a confrontation among animals of the same species, or in any kind of hostile dispute among humans.
Research and experimentation suffer from many methodological difficulties: usually a lack of ecological validity (similarity with natural conditions and stressors) or are not amenable to scientific investigation (difficult to test and verify).
Another is based on observations of animals in naturalistic settings, which avoids artificial environments and unnatural stresses, but usually does not allow the measurement of physiological effects or the manipulation of relevant variables.
In real life situations, animals (including humans) have to cope with stresses generated during their interactions with other members of their own species, especially due to recurrent struggles over the control of limited resources, mates and social positions.
[1][2][3] Social defeat is a source of chronic stress in animals and humans, capable of causing significant changes in behaviour, brain functioning, physiology, neurotransmitter and hormone levels, and health.
[6][7] Research also implicates that the referred behavioral effects are moderated by neuroendocrine phenomena involving serotonin, dopamine, epinephrine, norepinephrine, and in the hypothalamic-pituitary-adrenal axis, locus ceruleus and limbic systems.
[9] A useful concept in understanding the causal relationship between these behavioral and neuroendocrine effects is that of the 'causal chain', in which recurrent evolutionary events, in this case intra-specific competition, generate selective pressures that influence a whole species.
Evolutionary psychology provides several possible explanations for why humans typically respond to social dynamics in the way that they do, including possible functions of self-esteem in relation to dominance hierarchies.