It is not the similarity or dissimilarity of individuals that constitutes a group, but interdependence of fate. ~ Kurt Lewin
Human sociality is of interpersonal relationships with varying degrees of affinity bonding. As indispensably gregarious creatures, the humanity of humans relies upon having emotionally nourishing intimate relationships.
A dyad is a relationship between 2 people. It offers the greatest potential for intimacy.
A triad is a group of 3. Even the addition of a single member to a group, such as going from a dyad to a triad, alters interaction dynamics. Hence, having the same level of intimacy as readily achieved in a dyad is difficult in a triad.
Whereas the closest relationships provide emotional support, intimacy between members drops exponentially as group size rises. Small groups provide a sense of belonging. In contrast, larger groups can give a person the sense of being in a sea of people without much empathic connection.
Émile Durkheim termed the emotional discomfort of not belonging in a group anomie. Unless explicitly warmly welcomed, newcomers to a large group often experience anomie.
Regardless of size, the interaction dynamics of sustained groups are complex. Individuals create their social environment as well as being subject to and shaped by the social groups they encounter.
Individuals’ behaviors affect their social environments. When you pick your friends, it matters to you and it affects both what happens in the group and your behavior at a later time. ~ American evolutionary biologist Julia Saltz