and sociology began to emerge in the late 19th century. During this time theorists often included relationships into their current areas of research and began to develop new foundations which had implications in regards to the analysis of intimate relationships. Freud wrote about parent–child relationships and their effect on personality development. Freud's analysis proposed that people's childhood experiences are transferred or passed on into adult relationships by means of feelings and expectations. Freud also founded the idea that individuals usually seek out marital partners who are similar to that of their opposite-sex parent. In 1891, William James wrote that a person's self-concept is defined by the relationships endured with others. In 1897, Émile Durkheim's interest in social organization led to the examination of social isolation and alienation. This was an influential discovery of intimate relationships in that Durkheim argued that being socially isolated was a key antecedent of suicide. This focus on the darker side of relationships and the negative consequences associated to social isolation were what Durkheim labeled as anomie. Georg Simmel wrote about dyads, or partnerships with two people. Simmel suggested that dyads require consent and engagement of both partners to maintain the relationship but noted that the relationship can be ended by the initiation of only one partner. Although the theorists mentioned above sought support for their theories, their primary contributions to the study of intimate relationships were conceptual and not empirically grounded. 1960s and 1970s An important shift was taking place in the field of social psychology that influenced the research of intimate relationships. Until the late 1950s, the majority of studies were non-experimental. By the end of the 1960s more than half of the articles published involved some sort of experimental study. The 1960s was also a time when there was a shift in methodology within the psychological discipline itself. Participants consisted mostly of college students, experimental methods and research were being conducted in laboratories and the experimental method was the dominant methodology in social psychology. Experimental manipulation within the research of intimate relationships demonstrated that relationships could be studied scientifically. This shift brought relationship science to the attention of scholars in other disciplines and has resulted in the study of intimate relationships being an international multidiscipline. 1980s to 2000s In the early 1980s the first conference of the International Network of Personal Relationships (INPR) was held. Approximately 300 researchers from all over the world