Social cognition on the Internet: testing constraints on social network size

Abstract

The social brain hypothesis (an explanation for the evolution of brain size in primates) predicts that humans typically cannot maintain more than 150 relationships at any one time. The constraint is partly cognitive (ultimately determined by some aspect of brain volume) and partly one of time. Friendships (but not necessarily kin relationships) are maintained by investing time in them, and failure to do so results in an inexorable deterioration in the quality of a relationship. The Internet, and in particular the rise of social networking sites (SNSs), raises the possibility that digital media might allow us to circumvent some or all of these constraints. This allows us to test the importance of these constraints in limiting human sociality. Although the recency of SNSs means that there have been relatively few studies, those that are available suggest that, in general, the ability to broadcast to many individuals at once, and the possibilities this provides in terms of continuously updating our understanding of network members' behaviour and thoughts, do not allow larger networks to be maintained. This may be because only relatively weak quality relationships can be maintained without face-to-face interaction.

Figure 1.

Alternative hypotheses for the evolution of large brains in primates. Hypotheses differ in whether their central claim is about ontogeny, ecological or social processes, on whether they view food or predation as the rate-limiting process in population dynamics, and on whether they view the fitness benefits from large brains as being direct or indirect. Adapted from Dunbar [3].

Figure 2.

Mean change in self-rated emotional closeness (1–10 analogue scale) towards all unrelated friends for male (filled bars) and female (open bars) subjects as a function of their spending less or more time engaged in activities (shopping, going out, helping, going away) or in conversation (indexed as time since last contact face-to-face or by phone) at month 9 than they had at month 0. Adapted from Roberts & Dunbar [43].

Figure 3.

Mean rated happiness score (scale 0–10) for interactions with five best friends through six different communication media as a function of whether laughter occurred during the interaction (black bars) or not (grey bars). Laughter was recorded as both actual or virtual (e.g. the use of emoticons or acronyms such as LOL (‘laugh out loud’)). Interaction satisfaction was rated using Fordyce's [81] Happiness Measure on an 11-point Likert scale. Adapted Vlahovic et al. [80]. F2F, face-to-face; IN, instant messaging.