stress; if they are allowed to fight on several occasions, on different days, consecutive or not, it is regarded as a model of chronic stress. After the defeat or in the interval between fights, the subordinate animal may also be exposed to threats from the dominant one, by having to stay in a cage or compartment beside or nearby the dominant, exposed to its visual or olfactory cues. Later, the social defeat approach was also applied to observations of animal within-species aggression, in the wild, which suggested that the hypotheses generated on artificial laboratory settings can also be applied in observed in natural settings, confirming the predictions of the model. In humans It has been proposed that animal models of social conflict may be useful for studying a number of mental disorders, including major depression, generalized anxiety disorder, post-traumatic stress disorder, drug abuse, aggressive psychopathologies, eating disorders and schizophrenia (Bjorkqvist, 2001; Selten & Cantor-Graae, 2005; Rohde, 2001). The social defeat model has been extended to include observations of human aggression, bullying, relational aggression, chronic subordination and humiliation. The social defeat model attempts to extend animal studies to include human behaviour as well, in contrast to the social psychology study of aggression, in which comparisons are drawn exclusively from experiments involving humans (Bjorkqvist, 2001; Rohde, 2001). Bullying has interesting parallels with animal models of social defeat, the bully being equivalent to the dominant animal and the victim the subordinate one. At stake are possessions of material objects, money, etc., social position in the group, represented by in-group prestige, and the consequent lack of access to mates, including for socio-sexual behaviors like copulation. Human victims typically experience symptoms like low self-esteem (due to low regard by the group), feelings of depression (due to unworthiness of efforts), social withdrawal (reduced investments in the social environment), anxiety (due to a threatening environment), and they can also be shown to experience a plethora of physiological effects, e.g. increased corticosterone levels, and also a shift towards sympathetic balance in the autonomic nervous system (Bjorkqvist, 2001). Research about human aggression, usually conducted by psychologists or social psychologists, resembles to a great extent the research about social defeat and animal aggression, usually conducted by biologists or physiological psychologists. However, there is the problem of the use of different terminologies for similar concepts, which hinders communication between the two bodies of knowledge (Bjorkqvist, 2001). Similarly, research on depression has