The Theoretical Basis of the Complementarity Hypothesis
The complementarity hypothesis is the formal theoretical statement of the folk belief that opposites attract, and it was proposed systematically by Robert Winch in 1958. According to Winch's theory of complementary needs, people are drawn to partners who possess what they themselves lack, and the relationship takes hold because each person satisfies needs the other cannot satisfy alone. A dominant person is drawn to a submissive one, and someone who enjoys taking care of others is drawn to someone who needs to be cared for. The appeal of the theory lies in the way it explains attraction as an interlocking fit rather than as a matter of resemblance, so that difference becomes the reason for the bond instead of an obstacle to it. Winch's formulation has a natural affinity with psychoanalytic thinking, and it is sometimes linked to Carl Jung's concept of the shadow, in which a person projects onto another the unconscious aspects of the self that have gone unacknowledged. On that reading, attraction to an opposite is attraction to a disowned part of oneself, which gives the hypothesis an explanatory reach beyond the simple accounting of needs. The complementarity hypothesis is intuitively compelling, and the couple made up of opposites remains a popular theme in literature and film, where the contrast between the partners supplies both the conflict and its resolution. That cultural familiarity is one reason the hypothesis is so widely assumed to be established, and it makes the actual state of the evidence worth examining carefully rather than taking the idea on trust. Winch's own reasoning proceeded from the observation that a marriage is a division of functions as well as an emotional bond, so that partners who bring different capacities to the arrangement have more between them than partners who duplicate the same capacities. The needs he had in mind were relatively specific dispositions, including nurturance, dependence, dominance, and deference, rather than broad personality factors, and each was expected to find its counterpart in the other person. The theory thus makes a fairly precise prediction, namely that partners should be matched inversely on paired needs rather than merely differing from one another in some general way. That precision is useful, because it allows the hypothesis to be tested rather than merely illustrated with examples chosen after the fact.
Empirical Findings and Limited Support
The empirical record, however, provides only limited support for the complementarity hypothesis. As numerous meta-analyses have shown, similarity is consistently the stronger and more reliable predictor of interpersonal attraction and relationship satisfaction when relationships are examined in general terms. Complementarity nevertheless does appear to operate on specific dimensions, and the failure of the general hypothesis should not be read as its failure everywhere. The clearest evidence concerns the dimension of dominance and submissiveness. Research based on the interpersonal circumplex model shows that complementarity on this dimension, with one person taking the lead while the other follows, contributes to the smoothness of interaction, because the two are not competing for the same position within the exchange. There is also a case to be made for combinations of extraversion and introversion, where a complementary division of roles can function well: the extraverted partner takes the lead in social settings while the introverted partner provides the deep listening that sustains the relationship in private. The critical distinction to draw from this body of work is that complementarity functions on the dimension of behavioral style, whereas similarity holds the advantage on the dimensions of values and attitudes. Where partners differ in how they act, the difference can be organized into a workable division of labor. Where they differ in what they believe matters, no such division is available, and the difference presents itself repeatedly as conflict rather than as fit. The interpersonal circumplex clarifies why dominance behaves differently from other traits in this respect. The model arranges interpersonal behavior around two axes, one running from dominance to submissiveness and the other from warmth to hostility, and it predicts complementarity on the first while predicting similarity on the second. Dominant behavior invites deference and deference invites direction, so the pairing settles into a stable pattern, whereas warmth invites warmth and hostility invites hostility. This asymmetry within a single model is a useful corrective to the assumption that complementarity and similarity are rival theories competing to explain attraction in general. Each describes a different mechanism, and the productive question is not which is correct but which applies to the dimension under consideration.
Applying Complementarity in Compatibility Assessment
The same difference between two people can look like a division of labor on one day and a source of resentment on the next, and three distinctions do most of the work of explaining why it falls one way rather than the other. The first is to separate clearly the dimensions on which complementarity works from those on which similarity is what matters. Similarity is important for values, which are reflected in the values facet of openness, and for emotional stability, which corresponds to neuroticism. Complementarity can be effective for behavioral style, which includes parts of extraversion and parts of conscientiousness. Applying the wrong principle to the wrong dimension is one of the more common errors in interpreting a compatibility result. The second distinction is that complementarity should be understood as a combination of strengths rather than as the covering of deficits. One partner draws up the plan while the other adapts flexibly to circumstances; one keeps the larger picture in view while the other attends to detail. The evaluation is best framed in terms of how well the pair functions as a team. The third distinction is that complementarity only works when both partners recognize and respect their differences as strengths rather than as flaws. Where that precondition is missing, complementarity is experienced simply as incompatibility, and the same difference that could have been a division of labor becomes a standing grievance. Whether that third condition still holds is usually audible in the words spoken at home. As long as the trait can be described as the thing that saves you trouble, it is working as complementarity; once it turns into there they go again, the same difference has become a place to store grievances. Recalling what you were once glad the other person took care of, and saying it out loud once, is enough of a place to start. A comparison of the research evidence for the similarity hypothesis and the complementarity hypothesis is treated in detail in the article Similarity versus Complementarity: Which Pairing Lasts Longer.