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Instances of sustained cooperative behaviour in humans can be considered as an adaptive strategy that enhances the probability of reaching a goal. This study investigates psychophysiological responses to cooperation in healthy subjects, while considering outcome and gender as potential moderators of these responses. Salivary cortisol levels (Csal), heart rate (HR), skin conductance level (SCL), nonspecific skin conductance responses (NSRs), and mood states were measured at different points before, during and after a Lego house-building task in undergraduate men (n = 22) and women (n = 20). Once the task was finished, the experimenter informed the participants about the outcome obtained (positive or negative). Cooperation produces an increase in HR, SCL, and NSR responses. When the outcome is positive it produces a gradual diminution in Csal levels, but when the outcome is negative there is a significant increase in Csal levels after the task followed by a progressive decrease. Men with positive outcomes showed a lower area under curve (AUC) in Csal than women with a negative outcome. Men had more NSR responses in all periods other than the rest period. Several mood states are differently affected by the combined effect of outcome and gender. Our laboratory results can be generalized to other situations in which negotiation, mediation, and cooperative strategies are relevant for taking decisions and/or solving problems. The authors wish to thank Dr Tinca Polderman and John Rawlins for the revision of the English text. This study was supported by the Ministry of Business, Research and Science of the Valencia Regional Government (GVPRE/2008/260, GVACOMP/2010/250, and PROMETEO/2011/048) and the Ministry of Science and Education of the Spanish Government (PSI2008-04408/PSIC).

Hormonal and neuropsychological impairment in intimate partner violence (IPV) perpetrators could play a role in domestic violence. For characterizing whether there is a specific psychobiological response to stress, participants who had previously been jailed for IPV and controls were compared for testosterone and cortisol levels, tested for 2D:4D ratio (as an indicator of masculinization), and given several trait questionnaires and neuropsychological tests related to executive functions and theory of mind. After performing the Trier Social Stress Test (TSST), IPV perpetrators experienced decreases in salivary testosterone (T) levels, a moderate worsening of mood, slight anxiety, and a salivary cortisol (C) level increase. Moreover, high basal T was related with high levels of anger and anxiety and worse mood. However, that basal mood does not significantly alter T levels in response to stress. Nonetheless, controls experienced smaller changes in T and larger changes in C and psychological mood. With respect to neuropsychological and cognitive empathic features, IPV perpetrators showed poorer executive performance and emotional recognition than controls. In addition, deficits in both neuropsychological domains were positively associated. Regarding emotional empathy, IPV perpetrators showed higher levels of personal distress than controls. The 2D:4D ratio was lower in IPV perpetrators than in controls. Moreover, only in the former a smaller 2D:4D ratio was related to large increases in T in response to stress and poor emotional recognition. Together with social aspects involved in IPV, differences in psychobiological variables and their relationships could play a relevant role in the onset and perpetuation of violent behavior.