Do extraverts have more numerous and deeper social relationships? Organisations are increasingly interested in social capital, the networks accessed through individuals, so this is no idle question. Thomas Pollet from the University of Groningen, investigated this with University of Oxford collaborators Sam Roberts and Robin Dunbar, and their answer is yes, and no.
Recognising that our relationships aren't monolithic, the researchers treated social networks as a set of three layers. The inner support group contains those people (typically around five) that you would turn to in a crisis. Around this are a further ten-odd people, a sympathy group who would be deeply affected by your death. Finally there is an outer layer of more variable size, containing people connected to you by weak ties.
Pollet recruited 117 Dutch adults, who were asked to list their family, friends and acquaintances, and for each one, state the recency of communication and how emotionally close they were. Each network was grouped into layers, the innermost comprising those with past-week contact and over seven out of ten on the emotion measure; the sympathy layer those with past-month contact; and the outer layer receiving the rest. Each participant also completed a measure of extraversion.
The researchers found extraverts had more people in every layer – more weak ties, but also more individuals they contacted frequently. Although larger social networks have been reported before, this study finds the effect after controlling for age, a potential confound in other studies. However, extraversion didn't affect emotional closeness to their network: weak ties with occasional contacts don't appear stronger in extraverts.
The authors scrutinised every layer of the network, finding this same lack of effect throughout, but I'm cautious about interpretation at the inner layers, given that the emotional closeness score is both the variable of interest and the criteria used to determine membership. On my understanding, if introverts had a support group of contacts that they met frequently but gave low emotional closeness scores - fives or sixes - the methodology would never identify this.
It's worth noting the data suggests that regardless of extraversion, it's somewhat harder to keep close to all the members of a very large outer layer, which suggests a practical constraint that extraverts may be more liable to hit up against.
This study suggests extraverts have larger networks that are not simply populated by weak ties, but contain larger sets of close relationships. An organisation trying to tap into its social capital might start by talking to its most extraverted members. However, they shouldn't forget that introverts have equally deep relationships, nor that valuable networks contain the right people, not the most.
Pollet, T., Roberts, S., & Dunbar, R. (2011). Extraverts Have Larger Social Network Layers Journal of Individual Differences, 32 (3), 161-169 DOI: 10.1027/1614-0001/a000048