Consider Mr. C. He believes that, in the presence of uncertainty, the appropriate thing to do is to maximize the expected welfare. (Welfare is used interchangeably with net happiness. For simplicity, consider only choices that do not affect the welfare of others.) Suppose you put C in the privacy of a hotel room with an attractive, young, and willing lady. C can choose to go to bed with her or not to. C knows that the former choice involves a small but not negligible risk of contracting AIDS. He also calculates that the expected welfare of this choice is negative. Nevertheless, he agrees that, provided the lady is beautiful enough, he will choose to go to bed with her. This choice of C, though irrational (at least from the expected welfare point of view), is far from atypical. Rather, I am confident that it applies to at least 70% of adult males (the present writer included).

Yew-Kwang Ng, ‘Happiness, Life Satisfaction, or Subjective Well Being?’