The phenomenon social psychologists call "marital drift" — the gradual, often imperceptible divergence of two people who were once closely aligned — is among the most common sources of late-life marriage dissolution and one of the least discussed. It lacks the drama of infidelity or the clarity of abuse; it is simply the slow accumulation of years lived in increasingly separate interior worlds while sharing the same house.

The mechanisms are varied and interact in complex ways. Careers pull people toward different professional communities, different vocabularies, different ways of thinking about problems. Children absorb energy that couples once directed at each other and then, in departing, leave two people facing each other who have been functionally parallel rather than genuinely intimate for decades. Friendships and interests diverge. What felt like compatible temperaments in early adulthood can feel like incompatible personalities by sixty.

Research on marital satisfaction generally shows a U-shaped curve: highest in early marriage, declining through the child-rearing years, recovering somewhat after children leave, but not always recovering to its earlier heights. For some couples, the empty nest is a rediscovery; for others, it is a revelation that what they had been calling a marriage had long since become an arrangement.

Couples who maintain genuine intimacy across decades tend to share a few practices in common: they maintain some form of shared project or experience that creates new common ground; they talk about their inner lives as well as their shared logistics; they treat each other with the curiosity they once brought to learning who the other person was.

None of this is simple. All of it requires the kind of sustained intention that the routines of daily life consistently work against.