It was first proposed by anthropologist Robin Dunbar that there is a limit as to how many social relationships humans can maintain. Dunbar (1992) found a positive correlation between the brain size of primates and their average social group sizes. Dunbar then found the average human brain size, extrapolated the results of the primates, and predicted that the average social group size for humans is around 150 (now known as Dunbar’s number).
There is much evidence to support Dunbar’s prediction of 150 as the ideal social group number, looking at average group sizes. For example, Dunbar (1993) found that the average size of hunter-gatherer communities is 148, and the mean network size for Christmas card networks is 124.9 (Hill & Dunbar, 2003). Also, an example more relevant to modern life, the modal number of Facebook friends is 150-250 (Wolfram, 2013).
Dunbar has further divided these 150 relationships into groups based on closeness of relationship, using an expanding circles model. He suggested we have an inner circle, consisting of five ‘core’ relationships (close friends/kin). In the second circle, we have 15-20 friends and family. In the third circle, we have around 50 acquaintances, and in the outer circle we have familiars. In this model, the further the distance from the centre of the circle, the weaker and less intimate the relationship.
The reason for why we have such large social networks, Dunbar suggests, is due to our brain size. From an evolutionary perspective, living in large groups provides many advantages. For example, there are more eyes to look for predators, and large groups are more efficient at hunting, meaning more food for the group. Therefore, in the past, living in larger social groups would increase the likelihood of survival.
However, large social networks also have disadvantages. The main one being the amount of energy required to maintain our social relationships. Relationships are costly because they require a lot of time investment, and the strength of a relationship is a reflection of the amount of time invested in it. Roberts & Dunbar (2011) conducted a longitudinal study following 25 students for 18 months as they moved from school to university. They found that friendships were far more sensitive to decrease in contact frequency and number of activities done together than kinships. These results show friendships are much more costly to maintain than kinships, as they require more time and effort.
For primates, grooming is the primary method of bonding with each other. Grooming releases endorphins, which are rewarding and give a feeling of relaxation, building trust between primates. However, if humans were to bond with each other in the same way as primates, we would have to spend ̴43% of each day grooming each other (Dunbar, 1993). This clearly would not work, as we would have little time for anything else. Dunbar (1998) found that we only spend about 20% of our time on social interaction. Therefore, humans have had to develop more efficient, practical ways of bonding and maintaining closeness of relationships.
Some examples of how humans bond include religion, sport, music and dancing. Davis et al. (2015) conducted an experiment in which there were two groups of participants: one group doing low intensity exercise, and the other group doing moderate intensity exercise. After exercising, participants were asked if they would make a contribution to the group fund. It was found that participants in the moderate intensity condition donated significantly more than those in the low intensity condition. This is thought to be because the more exertive the activity, the more endorphins released, and therefore the more social bonds formed. Participants in the moderate intensity condition donated more money to the group fund as they felt a stronger connection and membership to the group.
Dancing also involves coordination with others, and especially synchronised dancing gives people a feeling of unity and connection with others. Tarr et al. (2015) investigated the effects of synchrony and exertion in dancing on the effects of social bonding. They found that highly exertive and highly synchronised dancing led to a significant increase in pain threshold (showing that endorphins had been released) and also had positive effects on in-group bonding, compared to low exertion dancing with only partial synchrony. As sports and dancing are both exertive activities, endorphins are released, and this has the same effect on relationships in humans as it does in primates.
Another activity involving highly synchronised behaviour is singing in a choir. Weinstein et al. (2015) recruited participants from a community choir that usually sang in small groups (20-80 people) but sometimes joined together to form a ‘megachoir’ of 232 people. Participants reported the degree of social bonding that they felt in each condition, and had their pain thresholds measured (to look for evidence of endorphin release). Researchers found that feelings of inclusion, positive affect and endorphin release increased with the number of rehearsals. Also, the large choir experienced a larger change in social bonding. Therefore, it was concluded that singing together leads to social bonding and increased closeness, even in large groups, and that music is very important for social bonding in humans.
Laughter also plays a large role in the social bonding of humans. Dunbar et al. (2011) found that laughter leads to a significant increase in pain threshold, which shows that laughter causes release of endorphins. Also, laughter leads to heightened affect, and feelings of wellbeing. For this reason, it is thought that laughter plays a crucial role in social bonding and maintaining relationships. Vlahovic et al. (2012) also found that out of all methods of communication, face-to-face contact and Skype lead to higher laughter rates than phone calls or texting, for example. Therefore, the best way to maintain relationships is through face-to-face contact and Skype.
In very large groups, activities such as sports, dancing and singing, especially synchronised, is not possible. However, large groups of people can still connect and feel a closeness with each other if they share things such as nationality, ethnicity and religion. Similarity leads to a greater degree of perceived social closeness, especially similar music taste, religion, and political views (Launay & Dunbar, 2015). Religion has always played an important role in bringing people together and forming communities, as people are united through shared beliefs. Also, the ideal size of a church congregation is under 200, which is further support for Dunbar’s number.
In conclusion, Dunbar’s prediction of 150 as the ideal social network size for humans seems to be accurate, as evidence such as the modal number of facebook friends and average Christmas card network sizes support this. There are several benefits to having large social networks from an evolutionary perspective, including more eyes to watch for predators, and larger hunting teams. However, maintaining relationships is costly as it requires a lot of time investment. Humans cannot afford to spend most of their time grooming each other like primates do. Therefore, we have had to find other activities to create social bonds. These are mostly exertive activities, such as sport and dance, as they release endorphins, which lead to feelings of relaxation and build trust with others. In very large groups, similar aspects of identity such as musical taste and religion can bond people.