In sociology, a peer group is both a social group and a primary group of people who have similar interests (homophily), age, background, or social status. The members of this group are likely to influence the person's beliefs and behaviour. Crowds are larger, more vaguely defined groups that may not have a friendship base. Crowds serve as peer groups, and they increase in importance during early adolescence, and decrease by late adolescence. The level of involvement in adult institutions and peer culture describes crowds.