An Overview of the Maturity Principle
The maturity principle is a regularity in personality development proposed by Brent Roberts and colleagues during the 2000s. It refers to the tendency for personality traits to change in socially desirable directions across the course of adulthood. Specifically, agreeableness and conscientiousness rise with age while neuroticism declines. Extraversion splits in two: social dominance, in the sense of assertiveness, tends to rise, whereas social vitality, in the sense of gregariousness, tends to fall. Openness peaks in young adulthood and then declines gradually thereafter. The direction of these shifts has been reported in common across a number of cultures. The magnitude of change varies from person to person, but its direction is broadly universal. The maturity principle is an important finding precisely because it runs against the common belief that personality does not change, and in the context of compatibility assessment it supplies a valuable perspective: a person's present personality is not necessarily the personality they will have in the future.
The Mechanisms Behind the Maturity Principle
Several explanations have been advanced for why the maturity principle holds. According to the social investment principle, the social roles acquired during adulthood, such as employment, marriage and raising children, drive personality change. Work demands conscientiousness, intimate relationships demand agreeableness, and increasing responsibility demands emotional stability. In the process of adapting to these roles, the corresponding traits are strengthened. The genetic maturation hypothesis suggests instead that part of this change reflects a developmental process that is genetically programmed. Twin studies indicate that genetic factors are involved in personality change as well. On the environmental side, the accumulation of life experience, improvements in interpersonal skill and a deepening of self-understanding all contribute as well. Maturation is not, however, automatic: how far someone engages with their social roles, and how much they take from what those roles teach, is thought to shape how much they change.
The Maturity Principle and the Long View of Compatibility
Taking the maturity principle into account changes how compatibility looks over a long horizon. First, an evaluation based on present personality profiles cannot fully predict future compatibility. If both partners' personalities shift in the direction of maturity, friction that exists now may well ease later on. A couple in which neuroticism runs high during their younger years may, for instance, become emotionally steadier with age and experience less conflict as a result. Second, because the rate of maturation differs between individuals, a temporary mismatch can arise when one partner matures earlier and the other later. Third, the relationship itself can become an environment that promotes maturation: a stable relationship functions as a secure base and supports a partner's growth. So it is worth looking at more than how well the two of you fit right now: whether the directions in which you are each changing line up matters too. Whether you are both trying to grow the same way, and whether each of you means to support the other in it, weighs heavily on compatibility seen over the long term.