Why Are Some People Annoying?

It doesn't happen often, but sometimes I just immediately dislike someone for no reason whatsoever. At my previous job I ended up working with a man I found amazingly annoying, even before he'd ever spoken to me. In the past I've just gone with it, but this time I thought I would try and understand why I felt this way about him, after all, I'd never met him and didn't know anything about him, so there shouldn't be any reason for me to feel that way.

Initially I made some discreet enquiries and found that other people felt the same way. So, at least I knew it wasn't just me. I decided to try and work out what it was about him that was so irritating, but nothing seemed to leap out. Now admittedly he did do some irritating things, the most annoying of which was sending me an email full of questions, despite sitting next to me, then immediately coming over and standing behind me and saying "I've sent you an email..." Then just staring at me while I waited for it to arrive, and read it, before thinking a bit and then answering him. So yes, that was annoying but crucially can't be counted here because I didn't know he did things like that when I first met him.

I never did work out what it was!