Defining Agreeableness and Its Facets
Agreeableness is one of the five factors of the Big Five model, and it measures the disposition to behave cooperatively, altruistically, and trustingly in relationships with other people. In the NEO-PI-R, agreeableness is broken down into six facets: Trust, Straightforwardness, Altruism, Compliance, Modesty, and Tender-Mindedness. People who score high on this dimension tend to read benign motives into the behaviour of others, to steer away from open conflict, and to place the needs of other people ahead of their own. Those who score low are more competitive and more sceptical: they give priority to their own interests and are willing to enter into confrontation when they judge it necessary. Agreeableness works as a lubricant in social life, but an extremely high score carries its own risks, including a tendency toward excessive self-sacrifice and difficulty in speaking up when one is being treated unfairly.
The Psychological Foundations of Empathy and Altruism
Empathy, which sits at the core of agreeableness, is normally understood as having two aspects: cognitive empathy and affective empathy. Cognitive empathy is the capacity to understand another person's point of view, while affective empathy is the tendency to feel another person's emotions as if they were one's own. People high in agreeableness tend to be high on both, but the affective component is especially pronounced. Altruism is the behavioural side that grows out of empathy: the inclination to help others without expecting anything in return. Evolutionary psychology accounts for altruism in terms of reciprocal altruism and kin selection, yet highly agreeable people are notably willing to act altruistically toward others to whom they are not related at all. How readily someone resonates with another person's feelings is thought to involve differences at the level of the brain as well, although which patterns of brain activity correspond to higher or lower agreeableness is still an open question.
Agreeableness and Compatibility Between Partners
Among the five factors, agreeableness is one of the strongest predictors of relationship satisfaction. Couples in which both partners score high on agreeableness have repeatedly been reported to experience less conflict, to adopt more constructive patterns of communication, and to be more satisfied with the relationship. How that quality actually shows up, though, varies with the combination of the two partners' levels. When both partners score high, a calm and cooperative relationship is comparatively easy to build; even when both score low, each partner can at least understand and accommodate the other's direct communication style. Trouble is far more likely when one partner is extremely high and the other is low, because such pairs slide into an asymmetric pattern in which the agreeable partner is always the one who concedes. So if you sense a wide gap between yourself and your partner here, it helps to read your disagreements as a difference in how each of you settles them rather than as a lack of goodwill on either side, and to check now and then whether the same person is always the one quietly giving way.