A not unreasonable definition of intelligence is that it is the ability to solve problems. If this is so, why are people with high intellectual ability not able to use their ability more effectively for solving everyday problems in living? Why are they not, by a wide margin, more effective than those who are less intellectually capable in achieving success in their occupations, in achieving better marriages, in successfully raising their children, and in achieving better mental and physical well-being? Examples abound of people with high intellectual ability who live their lives very foolishly and of people of ordinary intelligence who live their lives very well. Nor does one have to rely on informal impressions to come to the conclusion that intellectual ability is poorly correlated with success in living. Within the past decade, a considerable amount of research has been conducted on what has been referred to as practical intelligence. In a follow-up study of 100 Harvard students to their midlife, Vaillant (1977) found that intellectual ability was not significantly associated with any of his measures of adjustment, which included mental health, physical health, family relations, and success in work. It might be argued that the Harvard group was extremely selected, and that there was simply not enough range in intelligence to detect differences. Although the range of IQ was undoubtedly restricted, there was a considerable range of intellectual ability in the sample and a considerable range of success in living, so there was ample opportunity for a relation to be demonstrated if one existed. At the very least, one might have expected a significant, albeit small relation between intellectual ability and success in some domain. Yet, there was no evidence within any domain that intellectual ability was a significant predictor of success. The intellectually most gifted in college did not earn the most money if they became business executives, nor did they achieve the greatest recognition or productivity if they became professors.