Social status is a key regulator of reproductive behaviour in mammals. My research is divided into two distinct yet complementary programs investigating the interactions between sociality and sexually differentiated neural circuits and behaviours. First, I use a top-down approach to study how social status influences reproductive neural circuits in the naked mole-rat brain. These animals live in large colonies where reproduction is limited to a single female and 1-3 males; these breeders are socially dominant over all other animals, called subordinates. By comparing the brains of male and female subordinates and breeders, I have demonstrated that social status is more important than sex for determining morphology and protein expression in the brains of these uniquely social animals. Second, I use a bottom-up approach to study how sociality is affected when we “remove” sex differences in the brain. To do this, I study genetically modified mice that lack sex differences in neuron number, thus investigating how the absence of sex differences affect neural function and associated social behaviours. My recent data demonstrate that various sexually differentiated social behaviours are impaired in mice lacking sex differences in neuron number. By employing both approaches, my work reveals how social factors affect development and plasticity in the mammalian brain and, in turn, how specialized neural circuits control the expression of social behaviours.