You can't act like a sociopath if you're not one. But I would guess Meursault is a psychopath, not a sociopath. While both are antisocial, there has been some talk of prosocial or maybe neutrally social psychopaths who still don't feel things but also don't go out of their way to hurt people. They generally just want to leave people alone and be left alone in turn. But as you see in the novel, that's really not an option in our very social world.