Most of us belong to a number of different groups and perhaps would like to belong to
several others. When we are actively involved with a particular group, it generally functions as a reference group. As the situation changes, we may base our behavior on an
entirely different group, which then becomes our reference group. We may belong to many
groups simultaneously, but we generally use only one group as our primary point of reference in any given situation. This tendency is illustrated in Figure 7–1 .
Groups may be classified according to a number of variables. Four criteria are particularly useful: (1) membership, (2) strength of social tie, (3) type of contact, and
(4) attraction.