Formerly, I had always believed that class of origin had a big effect on people. Like a howitzer, favourable living and social circumstances propelled children on to success, while the more constrained circumstances of poor children cramped their style and shortened their ballistic trajectories, making them fall short in their achievements. So, social class of origin in childhood should influence and even determine social class attained in adulthood. Perhaps so.
If social class of origin has pervasive effects then they will show up in intelligence, behaviour and life styles. Here are two studies which come to somewhat different conclusions. Spot the differences.
Here are the conclusions of study A, of which points 1 and 2 are the most relevant.
Based on the results in the present study, it may be concluded that, at least among Swedish men: (1) high intelligence, an advantageous social background, and a high level of education are all positively associated with occupational and income trajectories, i.e. occupational position and income grow more steeply with age among those with high intelligence, a more advantageous background, and a high level of education than among those with lower scores, at least if analyzing development from young adulthood onward. (2) The effects of intelligence and social background on occupational and income trajectories are to a large degree mediated/accounted for by level of education. (3) High intelligence, an advantageous social background, and a high level of education are also positively associated with a deceleration of the increase in attained socio-economic position with age (a ceiling effect)
Here are the conclusions of study B
Childhood SES was found to explain a very small part of the relationship between IQ and health, which was similar to what was found for health at age 40 (Der et al., 2009). Given IQ in youth and childhood SES correlate strongly (r = .56), the extent of attenuation by childhood SES is less than would be expected. This suggests that childhood SES may not be a strong confounder of the relationship between IQ in youth and health outcomes in adulthood. Adult SES led to more attenuation than childhood SES. For example, looking at the average odds ratio across the self-report health conditions, which were significant in the baseline model, the effect size was reduced from an average OR of 0.75 at baseline, to 0.73 after adjusting for childhood SES, and to 0.90 after adjusting for adult SES. Adult SES tended to account for more of the relationship between IQ and most of the health outcomes than childhood SES did.
Yes, Study A is talking about occupational status and Study B about health, but let us look at the studies themselves, so as to resolve the apparent contradiction.
Study A is “Mediation of the gravitational influence of intelligence on
Kimmo Sorjonen, Tomas Hemmingsso, Ian J. Deary, BoMelina
The results are best shown in one figure, in which the high scorers on intelligence, social class of father and amount of education are compared to the low scorers.
The best outcome by age 40 is for those with most education, followed by those with high intelligence and then those with high class of origin. There is quite a gap before one comes to those with lowest class of origin, lowest education and finally lowest intelligence. The gaps between education levels and intelligence levels are large, the gaps between social class of origin smaller.
The paper gives SEM modelling results which show the relative contributions of each factor.
Study B is “Intelligence in youth and health at age 50”
These authors say: Higher intelligence in youth is linked with better physical health at age 50. Higher intelligence in youth is linked with lower risk for chronic illnesses. Adult but not childhood SES partially mediated the intelligence–health relationship.
Participants were the 5793 participants in the NLSY-79 who responded to questions about health outcomes at age 50. Sixteen health outcomes were examined: two were summary measures (physical health and functional limitation), 9 were diagnosed illness conditions, 4 were self-reported conditions, and one was a measure of general health status. Linear and logistic regressions were used, as appropriate, to examine the relationship between intelligence in youth and the health outcomes. Age, sex and both childhood and adult SES, and its sub-components – income, education, & occupational prestige – are all adjusted for separately.
Results & conclusion
Higher pre-morbid intelligence is linked with better physical health at age 50, and a lower risk for a number of chronic health conditions. For example, a 1 SD higher score in IQ was significantly associated with increased odds of having good, very good, or excellent health, with an odds ratio of 1.70 (C.I. 1.55–1.86). Thirteen of the illness outcomes were significantly and negatively associated with IQ in youth; the odds ratios ranged from 0.85 for diabetes/high blood sugar to 0.65 for stroke, per one standard deviation higher score in IQ. Adjustment for childhood SES led to little attenuation but adult SES partially mediated the relationship for a number of conditions. Mediation by adult SES was not consistently explained by any one of its components—income, education, and occupation status. The current findings contribute to our understanding of lower intelligence as a risk factor for poor health and how this may contribute to health inequalities.
General comment on class effects.
There are some complications when studying the effects of social class. Social class of origin is a mixture of what your parents achieved through their efforts, plus luck. Your social class of attainment is a mixture of what you achieve through your own efforts, plus what your ancestors were able to pass on to you, plus luck.
Exactly when you measure ability and status can make a difference. Testing the IQ of children before school maximises family influences. Testing IQ at school ages is a blend of family and school. Testing young adults is studying the finished product as it comes off the educational assembly line. All this ignores maturation effects, which may account for much of the IQ variation over childhood, regardless of experiences.
When should one assess attained social class? By convention, somewhere between 40 and 50 seems reasonable. After about 20 years of work your capacities to earn money, and to save it, should have become apparent. (You will have bought your most expensive house by age 47).
In my view we have a nexus. In historical terms our ancestors achieved things through their efforts, and passed on their genes and as much of their material advantages as they could to their children. Paper A shows the great effects of education, whilst also showing that it is intelligence linked (brighter students extend their education, because they enjoy it and can see the delayed advantages long term). Paper B suggests that class of origin contributes little to health. Attained social class is of course a consequence of skill and application, so the attenuating effect in the health paper is probably artefactual. What is curious is that class of origin contributes so little to later health. All those admonitions to brush your teeth have come to nothing.