  Humans use various social bonding methods known as social grooming, e.g. face
to face communication, greetings, phone, and social networking sites (SNS). SNS
have drastically decreased time and distance constraints of social grooming. In
this paper, I show that two types of social grooming (elaborate social grooming
and lightweight social grooming) were discovered in a model constructed by
thirteen communication data-sets including face to face, SNS, and Chacma
baboons. The separation of social grooming methods is caused by a difference in
the trade-off between the number and strength of social relationships. The
trade-off of elaborate social grooming is weaker than the trade-off of
lightweight social grooming. On the other hand, the time and effort of
elaborate methods are higher than lightweight methods. Additionally, my model
connects social grooming behaviour and social relationship forms with these
trade-offs. By analyzing the model, I show that individuals tend to use
elaborate social grooming to reinforce a few close relationships (e.g. face to
face and Chacma baboons). In contrast, people tend to use lightweight social
grooming to maintain many weak relationships (e.g. SNS). Humans with
lightweight methods who live in significantly complex societies use various
social grooming to effectively construct social relationships.
