why do we like some pple more than we like others?

why do i feel inclined to shout at some pple on the phone and not others. i hate it when pple call me when i'm in the midst of doing something. i guess they wouldn't know when to call otherwise since they don't keep tabs on me 24-7. but i don't think this is the problem. the problem, rather, is tt i feel hopelessly inclined to scream at only certain pple who call me during those pissable times. this implicit preference worries me.