Throughout the eighties evidence from a range of sources suggested that primate’s large brains were due to the cognitive demands of their complex social world. Evidence supporting this hypothesis came from Dunbar (1992), who demonstrated that social group size correlates with relative neocortex volume in primates, specifically the frontal lobes. This was due to the need for complex social skills, mainly tactical deception and coalition formation, which require advanced cognitive skills in their use of theory of mind (ToM) to predict others, behaviour (Dunbar 2003b). The aim of this study was to see if general intelligence (IQ), social intelligence (ToM), or head size, were correlated with social network size. Social network size was estimated using a 9-item questionnaire we created, and IQ was measured using part of the MAB-II test. ToM was assessed using the Revised Eyes Test (Baron-Cohen et al. 2001), and Picture Sequencing task, (Langdon et al.1999). Empathizing and systemizing have also been linked to social ability and are measured using the Empathy Quotient and Systemizing Quotient (Baron-Cohen et al. 2003). Empathy is the desire to understand and appropriately respond to others emotions and thoughts (Baron-Cohen 2002). Empathy was found to be the most significant predictor of social network size, which raises the possibility that it is not just intelligence dictating social network size, but also an interest in people. IQ was also significantly related to social network size supporting Dunbar’s (2006) belief that social intelligence is dependent on individual’s general intelligence. ToM and head size were not significant predictors of social network size.