Situation: Someone gets a 780 on his math SAT.
Nice guy: Never brings it up unless asked; feels he got lucky on the test.
Average guy: Brings it up in conversation whenever the subject is remotely appropriate. For a while asks others what they got in hopes that they will ask his score in turn, but soon realizes this is too transparent. His score boosts his self-confidence, and he secretly enjoys feeling superior to the 99.7% of the population which ranks below him.
Sociopath: Asks others their score, then announces his (rounding it up to 800) while scoffing at theirs. After a while he realizes that modesty would serve him better, but he looks so pleased with himself as he tells people it was nothing that they are put off by the blatant falseness of his modesty. The score has no notable effect on his self-confidence, as he considered himself far smarter than others even before.
Situation: At age 30, what does a guy's sexual resume look like?
Nice guy: Has slept with two women. Has dated others, some for extended periods, but never felt comfortable pushing for sex. Sees himself as a loser in the sexual sweepstakes game, and wonders how other guys get laid so often. (When other guys lie about their conquests, he believes them.) Former girlfriends remember him as nice guy, but boring.
Average guy: Has slept with six women, including the time he went to a prostitute. Has seen the statistics on this, and takes some comfort that he is right at the national average. Is considering proposing to his current girlfriend. But is torn because he is now much more confident in his ability to seduce, or at least not make a fool of himself with women, than he was at age twenty.
Sociopath: Has slept with forty women, including six whom he sort of date-raped. Sees himself as irresistible, even to those six. Does have an instinctive knack for knowing what to say to get women into bed. Secretly laughs at guys who feel they must be honest with women, and regards them as weak. Has no desire to get married or have kids unless he meets an heiress. If he does, and gets caught cheating, will declare himself a "sex addict," and go through the motions of seeking treatment. His exes regard him with varying levels of bitterness, that level being pretty much directly correlated with the amount of time they spent with him.
Situation: What does an average-looking guy think of his own appearance?
Nice guy: Sees himself as terminally unattractive; focuses on his flaws. On the rare occasions the subject comes up, he is almost apologetic about his looks. It never occurs to him to get plastic surgery.
Average guy: Sees himself as above average in looks. It has occurred to him to get plastic surgery to correct his flaws, but the thought of facing his buddies afterward is too embarrassing.
Sociopath: Has had plastic surgery, and taken steroids, and in fact is now better-looking than average. As far as his remaining flaws, sees them as imperfections that only make him more "interesting." In fact, every time he sees that Dos Equiis commercial about the most interesting man in the world, he thinks, bullshit, I'm way more interesting than that old fart.