he first leg of that argument has been established for many decades. In modern developed countries IQ correlates about 0.5 with measures of income and social status--a figure telling us that IQ is not everything but also making plain that it powerfully influences where people end up in life. The mean IQ of Americans in the Census Bureau's "professional and technical" category is 111. The mean for unskilled laborers is 89. An American whose IQ is in the range between 76 and 90 (i.e., well below average) is eight times as likely to be living in poverty as someone whose IQ is over 125.
Second leg: Intelligent people tend to be the most knowledgeable about health-related issues. Health literacy matters more than it used to. In the past big gains in health and longevity were associated with improvements in public sanitation, immunization and other initiatives not requiring decisions by ordinary citizens. But today the major threats to health are chronic diseases--which, inescapably, require patients to participate in the treatment, which means in turn that they need to understand what's going on. Memorable sentence in the Gottfredson-Deary paper in the February 2004 issue of Current Directions in Psychological Science: "For better or worse, people are substantially their own primary health care providers." The authors invite you to conceptualize the role of "patient" as having a job, and argue that, as with real jobs in the workplace, intelligent people will learn what's needed more rapidly, will understand what's important and what isn't and will do best at coping with unforeseen emergencies.
It is clear that a lot of patients out there are doing their jobs very badly. Deary was coauthor of a 2003 study in which childhood IQs in Scotland were related to adult health outcomes. A central finding: Mortality rates were 17% higher for each 15-point falloff in IQ. One reason for the failure of broad-based access to reduce the health gap is that low-IQ patients use their access inefficiently. A Gottfredson paper in the January 2004 issue of the Journal of Personality & Social Psychology cites a 1993 study indicating that more than half of the 1.8 billion prescriptions issued annually in the U.S. are taken incorrectly. The same study reported that 10% of all hospitalizations resulted from patients' inability to manage their drug therapy. A 1998 study reported that almost 30% of patients were taking medications in ways that seriously threatened their health. Noncompliance with doctors' orders is demonstrably rampant in low-income clinics, reaching 60% in one cited study. Noncompliance is often taken to signify a lack of patient motivation, but it often clearly reflects a simple failure to understand directions...
...And then there is the third leg of the IQargument: the lifestyle question. Smoking, obesity and sedentary living are more prevalent among low-status citizens. A 2001 study by the Centers for Disease Control & Prevention found that college graduates are three times as likely to live healthily as those who never got beyond high school. Not clear is what the government can do about this.