NATURE NEUROSCIENCE VOLUME 15 | NUMBER 5 | MAY 2012 681 Decades of animal research have provided a rich account of neuroendo- crinological influences on the social behavior of non-human animals. Inspired by these findings, human social neuroendocrinological research has flourished in recent years. Nevertheless, seemingly contradictory data, multi-leveled interactions and methodological hurdles have raised serious challenges. Here we summarize important findings in animal and human social neuroendocrinology, focusing on how roots in animal research have sprung new branches of human research. We then outline ways in which human research can con- tinue to profit from the methods and discoveries of animal research and ways in which human research offers unique opportunities for increasing our understanding of the social cognitive, affective and motivational processes underlying social neuroendocrinology. The neuroendocrinology of animal social behavior Neuropeptides (that is, oxytocin and arginine vasopressin, AVP) and steroid hormones (that is, testosterone and estradiol) have a central role in the social lives of animals. As comprehensive reviews on animal social neuroendocrinology have appeared recently 1–3 , we will only briefly touch on themes in this literature that have provided the roots for research in humans (Fig. 1). With that in mind, we focus on oxytocin, AVP and testosterone and their influences on four general categories: affiliation, social cognition, aggression and anxiety/stress responses. Although other hormones (such as estradiol) are important for animal social behavior, their effects on human social behavior are not well explored and will therefore not be reviewed here. Oxytocin and AVP perform social functions in a wide variety of species 2 and show remarkable evolutionary preservation of struc- ture and function 4 . Oxytocin has proven to be particularly critical for the expression of affiliative behaviors. Its involvement in mater- nal behavior is well established 2 . It also determines whether or not individuals of various rodent species engage in alloparental behav- ior 5 , the parenting of non-offspring. Oxytocin is also important for pair bonding and partner preference in a number of species. In prairie voles, a rodent that exhibits unusually monogamous pat- terns of behavior, oxytocin increases females’ preference for spe- cific partners and oxytocin antagonists decrease that preference 6 . Accordingly, extracellular concentrations of oxytocin increase (in the nucleus accumbens, NAcc) during mating in females and during parturition 7 . It is important to note that much of oxytocin function, particularly in regards to affiliative behaviors, is regulated by estro- gen’s influence on the expression of its receptors 8 . Mother-offspring bonding, pair bonding and partner preferences all rely on the ability of the animal to form a memory of the offspring or partner. Oxytocin is important for social memory in a variety of species 9 , determining scent-based memory in animals that rely on scents to identify conspecifics. It appears to be particularly important for the acquisition of social memories. Rats with a null mutation in their oxytocin gene, for example, regain social memory if they receive oxytocin centrally before their initial encounter with a target animal 10 . It may also facilitate maternal memory consolidation 11 . Oxytocin is not usually associated with aggression per se, although it appears to be involved in maternal aggression 12 . Finally, oxytocin moderates physiological stress responses and anxious behavior. In ham- sters, for example, high cortisol levels inhibit wound healing such that wound size is a gauge of the stress response and its effect on the body; oxytocin administration buffers the stress response such that wound size is decreased for isolated animals, whereas a centrally delivered oxytocin antagonist impairs wound healing in paired animals 13 . Data also demonstrate its anxiolytic qualities. Mice lacking the oxytocin gene exhibit more anxious behavior in their exploration of mazes 14 . AVP also affects affiliative behaviors 15 . In rats, AVP is implicated in paternal behaviors, such as grooming, crouching over and contacting pups 16 . AVP is also important for partner preference and pair bond- ing, particularly for males in a variety of species. Central adminis- tration of AVP in prairie vole males who have not mated triggers a selective preference for mates 15 . The distribution of AVP receptors in The animal and human neuroendocrinology of social cognition, motivation and behavior Cade McCall & Tania Singer Extensive animal and recent human research have helped inform neuroendocrinological models of social cognition, motivation and behavior. In this review, we first summarize important findings regarding oxytocin, arginine vasopressin and testosterone in the domains of affiliation, social cognition, aggression and stress/anxiety. We then suggest ways in which human research can continue to profit from animal research, particularly by exploring the interactive nature of neuromodulatory effects at neurochemical, organismic and contextual levels. We further propose methods inspired by the animal literature for the ecologically valid assessment of affiliative behavior in humans. We conclude with suggestions for how human research could advance by directly assessing specific social cognitive and motivational mechanisms as intermediate variables. We advocate a more comprehensive look at the distinct networks identified by social neuroscience and the importance of a motivational state, in addition to approach and avoidance, associated with quiescence and homeostatic regulation. Max Planck Institute for Human Cognitive and Brain Sciences, Department of Social Neuroscience, Leipzig, Germany. Correspondence should be addressed to T.S. (singer@cbs.mpg.de). Published online 15 April 2012; doi:10.1038/nn.3084 FOCUS ON SOCIAL NEUROSCIENCE REVIEW npg © 2012 Nature America, Inc. All rights reserved.