The Social Brain; An Investigation into Total Social Network Size and Relationship Closeness within a Distinct Human Population.
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The ‘Social Brain Hypothesis’ suggests that selection for the expansion of the neocortex in primate species is thought to originate from the cognitive demands posed by social living. Research into primates, has shown that neocortex size successfully correlates with social group size (Dunbar, 1992; 1993). Furthermore, evidence from multiple indices of social complexity, like tactical deception (Byrne & Corp, 2004), coalition formation (Plavcan et al, 1995; Kudo & Dunbar, 2001) and the size of intimate grooming cliques (Kudo & Dunbar, 1991) have all been found to correlate with the neocortex size. Thus the aim of the current study is to investigate whether head size, ‘social intelligence’, personality, empathy, systemizing and altruism correlate with measures of total social network size and relationship closeness in a distinct human population. In a sample of 124 participants, social network size was examined using an 8-item SNS (Social Network Size) Questionnaire and relationship closeness was assessed using the RCQ (Relationship Closeness Questionnaire) both measures were created for the specific purposes of this study. Following this, ‘social intelligence’ was measured using the V2 and P3 subtests of the MAB II; personality was measured using the standard NEO-FFI R and Rushton’s altruistic behaviour scale was employed to assess individual levels of altruism. Empathy and systemizing are also thought to be implicated in the formation of social relations (Wheelwright et al, 2006; Baron-Cohen & Wheelwright, 2004; Baron-Cohen, 2002; Baron-Cohen et al, 2001). Thus the EQ-short and the SQ-short (Wakabayashi et al, 2007) were used to measure individual’s empathy and systemizing levels. In support of Dunbar’s previous findings (Dunbar 1992; 1998) ‘social intelligence’ (emergent from ‘general intelligence’) was found to correlate with total social network size in humans: (r = .225, p <.05*, r² = .0506). Furthermore a significant correlation between altruism and total networks size was established (r = .248, p <.05*, r² = .0615). Finally extraversion was found to positively correlate with total network size (r =.475 p<0.01**) and relationship closeness scores of the support clique (r = .347 p< .01) and the sympathy group (r =.316 p<.01). As expected neuroticism negatively correlated with social network size (r = -.216, p<.05*). The present research provides a valuable first step towards identifying factors beyond individual differences in cognitive ability, as suggested by Dunbar (1998), which serve to constrain social group size and complexity in a human population.