"After all these years, they should know me"

A new partner might be forgiven for not knowing. But this is someone who's shared your bed, your bank account and your bad habits for a decade or more. They've seen you through a bereavement and two house moves. Surely by now they've learned to read you.

They've learned a lot. They know how you take your tea, which of your relatives you can't stand, and what you'll order in an Indian restaurant. They know most of the stable facts about you. What you need on a particular Sunday evening isn't that kind of fact. It depends on the week you've had, the mood you're in, and what you happen to want right now. What they learned in 2015 doesn't tell them that.

There's research on whether time together makes people better at knowing each other, and the answer is awkward. Swann and Gill studied dating couples, and separately followed room-mates over time. They measured how accurately each person could describe the other's history, preferences and views. They also measured how confident each was in those descriptions. The longer and closer the relationship, the more confident people were. They weren't consistently more accurate. People knew more about each other as time passed, in the sense of having a richer picture, and the richer picture made them surer. It didn't make them right more often.

That works against you in two ways. Your partner is confident they can read you, so when you say "fine" and seem roughly fine, they don't probe. You're confident they can read you too, so you don't see any need to spell it out. You're both relying on a skill that neither of you has.

Kenneth Savitsky, Boaz Keysar and colleagues found something that points the same way. They called it the closeness-communication bias, and the rest of their paper's title states the finding, which is "increased egocentrism among friends versus strangers". As that indicates, people were more likely to assume they'd been understood when they were talking to someone close than when they were talking to a stranger. With a stranger, you know you have to explain yourself. With a spouse you assume you don't, so you explain less, and you're understood less well than you think.

People also change. The person your partner learned to read ten years ago wanted different things. You may once have wanted to be left alone when upset, and now want company. You may never have said so. They're still applying the old rule, in good faith, and you take that as indifference.

Spending years with someone gives you affection and shared history and a good deal of knowledge about them. It doesn't let either of you see what the other is thinking. You're entitled to everything long acquaintance really provides. It was never going to provide that.