The tobacco plant originated in South America and spread to the rest of the world. Native Americans began cultivating two species of the tobacco plant (Nicotiana rustica and Nicotiana tabacum) about 8,000 years ago. The consumption of tobacco was unknown outside of the Americas until Columbus brought it back to Europe at the end of the 15th century. The consumption of tobacco is therefore evolutionarily novel, and the Hypothesis would thus predict that more intelligent individuals may be more likely to consume tobacco than less intelligent individuals.

The Hypothesis is confirmed with data from the United States but not the United Kingdom. The analysis of the National Longitudinal Study of Adolescent Health in the United States shows that, net of age, , race, , religion, marital status, , , earnings, political attitude, , general satisfaction with life, , frequency of socialization with friends, number of recent sex partners, childhood family income, mother’s education, and father’s education, more intelligent American children grow up to smoke more more frequently than their less intelligent counterparts.

The following graph shows the association between childhood intelligence and the latent factor for tobacco consumption. The bivariate association is curvilinear, not linear. Nevertheless, “normal” (90 < IQ < 110), “bright” (110 < IQ < 125), and “very bright” (IQ > 125) Americans are more likely to smoke cigarettes than their “very dull” (IQ < 75) or “dull” (75 < IQ < 90) counterparts. The overall association between childhood intelligence and the consumption of tobacco is positive. The more intelligent they are in junior high and high school, the more tobacco they consume as young adults seven years later.

In contrast, however, the analysis of the National Study in the United Kingdom shows that, net of a large number of social and demographic variables, more intelligent British children grow up to smoke fewer cigarettes throughout their adult lives in their 20s, 30s, and 40s than less intelligent individuals. The following graph shows the association between childhood intelligence and the latent factor for tobacco consumption. There is a clear monotonic negative association between childhood intelligence and adult tobacco consumption. The more intelligent they are before the age of 16, the less tobacco they consume in their 20s, 30s, and 40s.

There have been other studies that confirm these divergent patterns of association between and tobacco consumption in the two countries. These studies show that more intelligent individuals smoke more cigarettes than less intelligent individuals in the United States, but fewer cigarettes in the United Kingdom.

Why is this? Why would childhood general intelligence have opposite effects on adult cigarette consumption in the US and the UK? I speculate about possible reasons in my next post.