All animals and people are like this. When my mean cat (Egan) eats, he doesn't want my other cat (Wizard) to eat with him. Egan gets aggressive and scares Wizard away. ... Egan doesn't want me to pet him because he doesn't like me. It's only because he doesn't want to be touched. Stupid furball! Egan's supposed to love me. And whenever I wanna see him, he turns away. Doesn't want anything to do with me. Stupid cat.

As much as I, or most people for that matter, don't like this trait, I think each of us depending on the situation can be selfish. If I'm eating a big all meat burrito and I see you looking at my burrito with lust, and you ask me for a bite, I'm going to have to do the selfish thing and say no. It's the right thing to do under the circumstances.