groups include reciprocal altruism, deception and coalition formation. These group dynamics relate to Theory of Mind or the ability to understand the thoughts and emotions of others, though Dunbar himself admits in the same book that it is not the flocking itself that causes intelligence to evolve (as shown by ruminants). Dunbar argues that when the size of a social group increases, the number of different relationships in the group may increase by orders of magnitude. Chimpanzees live in groups of about 50 individuals whereas humans typically have a social circle of about 150 people, which is also the typical size of social communities in small societies and personal social networks; this number is now referred to as Dunbar's number. In addition, there is evidence to suggest that the success of groups is dependent on their size at foundation, with groupings of around 150 being particularly successful, potentially reflecting the fact that communities of this size strike a balance between the minimum size of effective functionality and the maximum size for creating a sense of commitment to the community. According to the social brain hypothesis, when hominids started living in large groups, selection favored greater intelligence. As evidence, Dunbar cites a relationship between neocortex size and group size of various mammals. Criticism Phylogenetic studies of brain sizes in primates show that while diet predicts primate brain size, sociality does not predict brain size when corrections are made for cases in which diet affects both brain size and sociality. The exceptions to the predictions of the social intelligence hypothesis, which that hypothesis has no predictive model for, are successfully predicted by diets that are either nutritious but scarce or abundant but poor in nutrients. Researchers have found that frugivores tend to exhibit larger brain size than folivores. One potential explanation for this finding is that frugivory requires "extractive foraging", or the process of locating and preparing hard-shelled foods, such as nuts, insects, and fruit. Extractive foraging requires higher cognitive processing, which could help explain larger brain size. However, other researchers argue that extractive foraging was not a catalyst in the evolution of primate brain size, demonstrating that some non primates exhibit advanced foraging techniques. Other explanations for the positive correlation between brain size and frugivory highlight how the high-energy, frugivore diet facilitates fetal brain growth and requires spatial mapping to locate the embedded foods. Meerkats have far more social relationships than