Intimacy and self-disclosure are important features of friendships in child hood and adolescence. Most theorists and researchers have considered the two features to be highly related, if not synonymous. Sullivan (1953), one of the first theorists to emphasize the importance of intimate friendships, argued that the emergence of such friendships during later childhood has a powerful influence on personality development. He defined intimacy as “closeness, without specifying that which is close other than the persons” (1953, p. 246). Sullivan further suggested that intimacy was partly the result of self-disclosure. Also, he argued that self-disclosure to friends has positive effects on children's personalities. For example, he proposed that conversations with friends help children gain a better understanding of themselves and other people. More generally, Sullivan assumed that intimate friendships involving frequent self-disclosure have positive effects on children's social development.

Most researchers who explore adults' relationships agree with Sullivan that intimacy and self-disclosure are closely related and have positive effects on individuals. Clark and Reis (1988), for example, defined intimacy as “a process in which one person expresses important self-relevant feelings and information to another, and as a result of the other's response comes to feel known, validated (i.e., obtains confirmation of his or her world view and personal worth), and cared for” (1988, p. 628).