"They know I'm busy"

You're busy, and your friend knows you're busy, and so the silence, you assume, arrives at their end with a label on it. Busy. Not ignoring me. Not gone off me. Just busy. Which is what it is. The belief is that the meaning of your silence travels with it.

It doesn't. Yoram Kalman and Sheizaf Rafaeli looked at what people make of a slow reply in a setting where the stakes were clear. Managers evaluated job candidates who'd taken different lengths of time to answer an email, a day, two weeks, or silence for over a month. The slow replies were read as a violation of what was expected, and how the candidate was judged depended on how the delay was read. The researchers describe response time as a nonverbal cue, one of the few available in writing, and they define online silence in terms of the norms it breaks. That's a hiring study, not a friendship study, and I'm extending it. But the point it makes about writing is general. When you talk to someone, your busyness is visible. In a message, the only thing that arrives is the time it took, and time on its own has no label.

Think about how you read it from the other side. A friend takes nine days to answer something you sent. You don't think "busy" for nine days. You think busy for two, then you think nothing for three, then you wonder whether the thing you sent was somehow wrong, then you tell yourself not to be daft, and then you stop expecting a reply and adjust. Your friend does exactly this with your silence, with one difference. They can't see the week you had. They can see the stretch.

There's a further problem with "they know I'm busy". It's true of everyone. Your friend is busy too. So is the cousin, and the person from the old job. Busy isn't a fact about you that explains your silence. It's a fact about adults that explains everyone's, and if it were a good enough reason, nobody would ever hear from anyone. What distinguishes the friends who stay in your life from the ones who thin out isn't that some were less busy. It's that some of them, or you, answered anyway, in the time they had rather than the time the reply deserved.

I'm not saying your friend is hurt. Most of the time they're not, or not much. I'm saying the silence arrives without the label, and the friend supplies their own, and you don't get to choose what it says.