This chapter concerns life's major decisions. Major decisions include medical decisions like the one at the beginning of this chapter, whether to marry, whom to marry, if and when to have children, what kind of occupation to choose, how to spend your hard-earned dollars, and so forth. Whether to marry, whom to marry, if and when to have children, what kind of occupation to choose, how to spend once hard-earned dollars, and so forth. Although avoidance is one way of handling stressful decisions, it is seldom a good way. Usually decisions have to be made with missing information and involve guesses and predictions about future events. Decisions very often involve probabilistic information, and decision-making errors using probabilities, like the one described here, are prevalent in the everyday thinking of people from all walks of life. The psychological literature is full of other examples of the influence of reciprocity on decisions.