Loners constitute an other crowd present at any science event, and like the celebrities, and raising stars, they are quite easy to spot.
- They generally stand alone in corners or secondary rooms
- They play games on their phones when everyone else is socializing or hanging out at the coffee break
- They might give awkward glares
- They might try to form a little group of loners at some point
This is harsh, but nobody notices them, knows their names, or even really wants to. I believe science attracts and somehow selects for people with poor or akward social skills, so it’s better to get used to them.
As a nice person, you can make a communication attempt by reaching out to them with a basic conversation opener : “The coffee taste so bad here, no ?”, “How boring was that last talk ?”, “Hey, where do you come from ?”, “May I borrow your pen ?” … bla bla bla. Despite all the efforts, please do realize that it will still probably result in a 5-minute conversation with lots of awkward silences and little eye contact.
PhD-bility 
I like the humour :D. As someone with loner tendencies, though, I’d like to say that I often desire to be alone so I don’t wish for people to talk to me. That being said, I probably won’t reject them.