Obviously, you glibly reply, it’s worth taking an interest in people. Especially the people you see regularly. These are the people who make up your life, and knowing what they like, what they don’t, what they’d love to help us with, what they’d love help with, is all just the way you do it.

But almost everyone has “invisible people” in their life. Maybe it’s everyone just beyond the ten people you’d “do anything” for. Maybe it’s only the cleaning person at the shop you go to every once in a while. I’m confident, though, that no one, not even the most extroverted can confidently claim that no one is below their radar. That they know as much as they could about everyone they ever share a room with.

Now I’m probably the last person in the world to tell you that’s a problem. I’ve spent most of the last decade glibly considering almost everyone in my life below my radar. And even as I’m feebly endeavoring to change that pattern, I still do it quite a lot. I’m introverted and shy. It’s a convenient excuse, but it’s also true.  Making conversations that don’t feel totally necessary is not my strong-suit. It’s not really my suit at all.

And there’s also the practical argument: do we really have time to get to know everyone we encounter? Maybe, when you’d cross paths with 100 people in the course of a year it made sense to get to know them all. But today, when the average pedestrian commuter in some cities brushes past more people on the way to work than a serf would encounter in her entire life, you just can’t do it. Attention doesn’t scale.

I’m not going to spend time disputing those points: after all, they’re essentially correct. There are reasons, both personal and practical, that some people are below your radar, that some people will always be below your radar. It’s not a problem that we’re selective about our attention—no one is happier than I when America looks away from the dumb Reality TV sensation of the week and gives a bit of attention to things that matter—but I just think we should acknowledge that we’re doing it.

And I think it’s useful to bring some curiosity to what’s below our radar. Why are we spending our time on this? Why aren’t we spending our time on that? There aren’t right and wrong answers to these questions. But that’s precisely why they’re worth spending some time with.