Sunday, 8 June 2014

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.


  1. I'm always amazed that people think they are "controlling for" income or SES by matching two subpopulations with very different population means in another characteristic (say IQ). If the two characteristics are highly correlated then for one subpopulation the income or SES characteristic is a low-probability event and therefore an outlier.

  2. Yes, Twain certainly does seem representative of a pattern. Just confining ourselves to America, one is hard put to find an example of a significant author who stayed on the farm:

    Benjamin Franklin: Thorough city boy. Boston, Philadelphia, London, Paris.

    Washington Irving: New York, London, Madrid, Paris, etc

    Hawthorne: born in Salem, but lived much of his life in fairly close proximity to Boston. Lengthy sojourns in Liverpool and Italy.

    Melville:Lived the bulk of his life orbiting around the Boston-NY area.

    Poe: Baltimore, Philadelphia, NY, Richmond, etc

    Henry James: New York, Boston, Newport, London, etc

    Walt Whitman: NY

    Emily Dickinson: Possible exception to the rule, as she lived out her life in rural Amherst, but the presence of Amherst college (her alma mater ) means that we should probably think of her as living in a university town.

    Eliot: St. Louis, Boston-Cambridge, London.

    Willa Cather: Although thought of as the chronicler of the rural West, spent the bulk of her career in NY.

    Hemingway: Oak Park (Chicago suburb), Chicago, Toronto, Paris.

    Fitzgerald:Grew up in provincial cities like St Paul, but was educated at Princeton. Later lived in Paris and LA.

    Off-hand, the only genuine counterexample that springs to mind is Faulkner. He basically stayed put in Oxford, MS, barring a few Hollywood sojourns (he worked on the screenplay for THE BIG SLEEP). Of course, Oxford is the home of the University of Mississippi,so perhaps we should slot him alongside Dickinson as an author who lived out his life in a university town.


  3. Updike only spent a few years in New York City, then moved to exurban Massachusetts well north of Boston -- an area of expensive, very old small towns with well-educated locals.

    Flannery O'Connor was, I believe, a small town stay at home.

    Nabokov mostly lived in Ithaca, NY to teach at Cornell, then moved to an expensive hotel in Switzerland.

  4. One question is how many of the major American writers started out growing up below the well-educated class? I suspect fewer than we'd guess.

    Okay: try 2 Southerners who moved to the New York City area: Thomas Wolfe and Tom Wolfe. Thomas was from an upwardly mobile skilled working class background. His father ran a gravestown carving business and his mother ran boarding houses and eventually made a fair amount of money in real estate.

    But Tom Wolfe came from the educated upper middle class. His father was a professor of agronomy and editor of "The Southern Planter" magazine. Tom Jr. assumed as a boy that the Thomas Wolfe novels on the shelves had been written by his father.

  5. " (12 percentile points higher ability among those moving from rural areas to central cities compared to those staying in rural areas)"

    So, roughly, people who move from rural area to bright lights big city are at the 56th percentile of rurals and those who stay are at the 44th percentile? That's not really as big of a gap as I might have expected.

    1. Agree the gap seems small, but we have not been given the actual scores. For example, 98th percentiles definitely move, 86th percentiles might enjoy their relative local advantage. Wish authors would go back to simple, informative statistics.

  6. They should have controlled for Parent's socioeconomic status, not the children's.