Complementarity of roles is chiefly responsible for the degree of harmony and stability obtaining in interpersonal relationships (Spiegel, 1957). Collins et al. (1971) compared decision-making in the marriages of a group of male neurotics and in a control group. They found that patient marriages were more often categorized as ‘segregated’ (where distinct areas of responsibility were demarcated for each spouse) or ‘husband-dominated’ (where most of the decisions were made by the husband). Conflict over decision-making was also commoner in the patient marriages. By contrast, the control marriages were more often co-operative (both partners collaborated equally in a co-operative manner). The authors suggested that the severity of the husband's neurosis led to the adoption of certain patterns of decision-making which in turn led to conflict. They proposed that these patterns of behaviour might partly explain the development of psychiatric symptoms in the patient's spouse. In a series of normal families in Australia, Herbst (1954) noted that as the percentage of separate decisions increased tension rose. The ‘syncratic’ family structure (comparable to the co-operative pattern) was below average in tension, while the ‘autocratic’ (comparable to the segregated pattern) carried the highest tension.