Where the bright kids go

 

Years after he had left his childhood town of Hannibal, Missouri, Mark Twain returned, a successful writer, but not yet someone who would be recognised on sight. He asked a stranger after a number of his childhood friends, and finally innocently included his own name, Samuel Clements, in the list and asked what had become of him. His interlocutor replied: “Same as all the ones who did well, he went to St Louis and did well”.

In fact Mark Twain had gone, in succession, from Hannibal to New York City, Philadelphia, St. Louis, and Cincinnati, but from the parochial viewpoint of Hannibal, St Louis was where the bright kids went. Now the general observation that bright kids leave to the bright lights has been tested by Markus Jokela.

Flow of cognitive capital across rural and urban United States. Intelligence Volume 46, September–October 2014, Pages 47–53

DOI: 10.1016/j.intell.2014.05.003

Jokela has mined the 16-year longitudinal data from the U.S. National Longitudinal Survey of Youth 1979 (NLSY79) to examine whether cognitive ability assessed at age 15–23 predicted subsequent urban/rural migration between ages 15 and 39 (n = 11,481). Higher cognitive ability was associated with selective rural-to-urban migration (12 percentile points higher ability among those moving from rural areas to central cities compared to those staying in rural areas) but also with higher probability of moving away from central cities to suburban and rural areas (4 percentile points higher ability among those moving from central cities to suburban areas compared to those staying in central cities).

The sample of the present study included all participants for whom data on cognitive ability were available (assessed in 1980) and who had participated in at least one follow-up study after that between 1980 and 1996 (n = 11,481 unique individuals with up to 129,424 person-year observations over the follow-up period).

Socioeconomic status was measured with two separate variables of the highest completed education and household income assessed at each follow-up phase. The participants reported their highest completed grade on a 20-point scale (range from 1 = no education to 20 = 8th year of college or more) and household income as the total net household income from all income sources of the participant and her/his spouse in the past calendar year

First of all, this is a great sample. With numbers like these, and the nationally representative sampling, we can be reasonably sure of the results. Second, the fact that intelligence was tested early in life allows us to consider it as a putative cause of later achievements, including educational achievement and the income gained in employment. Third, this study looked at changes of address and required proof of residence, not just later recall, which strengthens the observed results. Although this is a study of the effects of intelligence on mobility, personality factors (not measured here) could also be contributors.

Studies of personality and residential mobility have demonstrated that psychological characteristics may contribute to selective migration, including rural-to-urban migration (Camperio Ciani et al., 2013,Duncan et al., 2012 and Jokela, 2013). For example, neuroticism and openness to experience have been associated with higher migration probability (Camperio-Ciani and Capiluppi, 2011, Jokela, 2013 and Silventoinen et al., 2008), extraversion has been associated with rural-to-urban migration (Camperio-Ciani and Capiluppi, 2011 and Jokela et al., 2008), and conscientiousness and agreeableness have been associated with lower likelihood of leaving current residence (Jokela, 2009 and Jokela, 2013).

The first analysis examined the average cognitive ability level by the interaction effect between categorically coded 1980 baseline location and subsequent location after 1980, adjusted for sex, race/ethnicity, birth year, subsample, and time-varying age.

Here we go again. That adjustment would make any sex and racial intelligence differences disappear. This loses a item of interest: is there an IQ premium for women and minorities? Simple means and standard deviations would have helped orient the reader before doing the adjustments

The author explains his procedure: These two analyses were thus conducted with cognitive ability as the outcome variable, and with the residential categories and their interaction effects as the independent variables, adjusted for covariates (my emphasis).

 

 

So, IQ has a big effect, but when you take away the socioeconomic status which is a consequence of your intelligence, the effect of intelligence is apparently diminished. Well, it would be, wouldn’t it? Socioeconomic status was not handed out by some perverse deity in the sky: employers evaluated the applicants on offer, and selected those most likely to help them achieve their objectives.

However, Jokela says: Adjusting for socioeconomic status in adulthood substantially attenuated the associations between cognitive ability and selective migration. This suggests that underlying cognitive-ability differences get differently distributed across rural and urban areas largely because educational attainment and household income are related to selective urban/rural residential mobility (i.e., mediation effect).

I don’t understand what is meant here. Clearly, you cannot move to a more agreeable place unless you have the money to do so. You will not get the money unless you flourish in a job for which you are qualified. You cannot get qualified unless you have the ability to complete your studies. You cannot graduate unless you pass the exams, which will be due to ability and diligence. The measures of ability were taken early in life, so they have not been caused by later socio-economic status or later educational qualifications. Education is the conveyor belt. Intelligence is the engine. Socioeconomic status has not attenuated the effects of intelligence. It is a consequence of intelligence.

Bright kids move from the farm to the city, and from thence to the leafy suburbs. As in Pompeii and the villas of Herculaneum.

Although the author does not mention it, most minorities drift towards cities. For example, in UK survey data on sex, if the classification of homosexuality nationally is about 4% (I think that was defined as a same sex relationship in the last 5 years) then the figure for London is 8%. If partners are hard to find, best to go to a central meeting place. Same for bright people, who are 2% nationally, and an unknown but probably higher percentage in London. Some drift to provincial university towns, few stay on the farm.

The mobility patterns associated with cognitive ability were largely but not completely mediated by adult educational attainment and income. The findings suggest that selective migration contributes to differential flow of cognitive ability levels across urban and rural areas in the United States.

There is a lot to like about this paper. Excellent, large and representative sample. Good measures of intelligence and long follow ups. However, I am not one to let a noble researcher leave uninjured: why “attenuate” for income without discussing the underlying assumption behind such a move? There is a case for controlling for parental income, but the bright person’s income is their own, earned by them. Equally, they gained educational qualifications because they had the ability and completed the course. Attenuate if you must, but only with care for the underlying logic.

I still remember the sunlight in the room at home in the countryside where I read Twain’s collected works. My favourite was his great American novel The Adventures of Huckleberry  Finn. I am still floating on the raft of his genius.