Influence of Intelligence on Social Mobility: Can Your IQ at the Age of 11 Predict Your Social Class at Midlife?

Written by Nea Lulik, MSc in Psychology of Individual Differences

Social status attainment and therefore social class mobility in adulthood are of interest to psychologists, sociologists, political scientists, economists, epidemiologists and many more. The reason behind the interest is because it indicates access to material goods, educational opportunities, healthy environments, and nonetheless the economic growth. It is important to study childhood ability, childhood social background, and education because they are important determinants to adult social status (Deary, et al., 2005) (Deary, Whiteman, Starr, Whalley, & Fox, 2004) (Johnson, Brett, & Deary, 2010b) (Johnson, Brett, & Deary, 2010a) (Breen & Goldthorpe, 2001) (von Stumm, Gale, Batty, & Deary, 2009).

Deary and colleagues (Deary, et al., 2005) did a study that encompassed a wide range of data of individuals in lifetime (in childhood and during mid-adulthood). Most of the Scottish children which were born in 1921 participated in the Scottish Mental Survey 1932, which was conducted under the auspices of the Scottish Council for Research in Education (SCRE, 1933) and obtained the data of psychometric intelligence of Scottish pupils (Deary, Whiteman, Starr, Whalley, & Fox, 2004). The number of children who took the mental ability test (based on the Moray House tests) was 87,498. They were between age 10 and 11. The tests covered general, spatial and numerical reasoning.

At mid-life period, a subset of the subjects participated in one of the Midspan studies, which were large health studies of adults and were carried out in Scotland in the 1960s and 1970s. The particular Midspan study they took part in was the Collaborative study of 6022 men and 1006 women, conducted between 1970 and 1973 in Scotland. Participants completed a questionnaire (participant’s address, father’s occupation, the participant’s own first regular occupation, the age of finishing full time education, number of siblings, and if the participant was a regular car driver) and attended a physical examination (measurement of height). Social class was coded according to the Registrar General’s Classification (1966) for the participant’s occupation at the time of screening, his first occupation and his father’s occupation. Six social classes were used (I – professional to V – lowest, manual work). Women were excluded from the data set due to the unrepresentativeness of the social spectrum.

A correlation and structural equation model analysis was conducted (Deary, et al., 2005). In the structural equation models, social status in the 1970s was the main outcome variable. The main contributors to education (and first social class) were father’s social class and IQ at age 11, which was also found in a Scandinavian study (Sorjonen, Hemmingsson, Lundin, & Melin, 2011). This effect was direct and also mediated via education and the participant’s first job.

Participants at midlife did not necessarily ended up in the same social class as their fathers (Deary, et al., 2005). There was social mobility in the sample: 45% of men were upwardly mobile, 14% were downwardly mobile and 41% were socially stable. IQ at age 11 had a graded relationship with participant’s social class. Same effect was seen for father’s occupation. Men at midlife social class I and II (the highest, more professional) also had the highest IQ at age 11. Height at midlife, years of education and childhood IQ were significantly positively related to upward social mobility, while number of siblings had no significant effect. For each standard deviation increase in IQ score at the age 11, the chances of upward social mobility increases by 69% (with a 95% confidence interval of 30% to 120%). After controlling the effect of independent variables, only IQ at age 11 was significantly inversely related to the downward in social mobility. Which means that more years of education help a man to surpass his father’s social class, and that low IQ makes a man prone to fail behind his father’s social class.

Higher IQ at age 11 was also significantly related to higher social class at midlife, higher likehood car driving at midlife, higher first social class, higher father’s social class, fewer siblings, higher age of education, being taller and living in a less deprived neighbourhood at midlife (Deary, et al., 2005)(see figure above). IQ was significantly more strongly related to the social class in midlife than the social class of the first job.

Finally, height, education and IQ at age 11 were predictors of upward social mobility and 0nly IQ at age 11 and height were significant predictors of downward social mobility (Deary, et al., 2005). Number of siblings was not significant in neither of the models.

Another research (Johnson, Brett, & Deary, 2010a) looked into the pivotal role of education in association between ability and social class attainment through three generations (fathers, participants and offspring) using the SMS1932 (Deary, Whiteman, Starr, Whalley, & Fox, 2004)(Lothian Birth Cohort 1921) educational data, childhood ability and late life intellectual function data. It was proposed that social class of origin acts as a ballast (Johnson, Brett, & Deary, 2010a), restraining otherwise meritocratic social class movement, and that education is the primary means through which social class movement is both restrained and facilitated – therefore acting in a pivotal role.

It was found (Johnson, Brett, & Deary, 2010a) that social class of origin predicts educational attainment in both the participant’s and offspring generations. 

Father’s social class and participant’s social class held the same importance in predicting offspring educational attainment – effect across two generations. Educational attainment mediated the association of social class attainments across generations (father’s and participants social class, participant’s and offspring’s social class). There was no direct link social classes across generations, but in each generation educational attainment was a predictor of social class, which is consistent with other studies (Nettle, 2003) (Forrest, Hodgson, Parker, & Pearce, 2011). Also, participant’s childhood ability moderately predicted their educational and social class attainment (.31 and .38). Participant’s educational attainment was strongly linked with the odds of moving downward or upward on the social class ladder. For each SD increase in education, the odds of moving upward on the social class spectrum were 2.58 times greater (the downward ones were .26 times greater). Offspring’s educational attainment was also strongly linked with the odds of moving upward or downward on the social class ladder. For each SD increase in education, the odds of moving upward were 3.54 times greater (the downward ones were .40 times greater). In conclusion, education is very important, because it is the fundamental mechanism functioning both to hold individuals in their social class of origin and to make it possible for their movement upward or downward on the social class ladder (Johnson, Brett, & Deary, 2010a).

In the Cohort 1936 it was found that regarding whole generations (not individuals) (Johnson, Brett, & Deary, 2010b) the social mobility between father’s and participant’s generation is: 50.7% of the participant generation have moved upward in relation to their fathers, 22.1% had moved downwards, and 27.2% had remained stable in their social class. There was a lack of social mobility in the offspring generation as a whole. However, there was definitely individual offspring movement on the social class ladder: 31.4% had higher social class attainment than their participant parents (grandparents), 33.7% moved downward, and 33.9% stayed stable. Participant’s childhood mental ability was linked to social class in all three generations. A very important pattern has also been confirmed: average years of education increased with social class and IQ.

There were some great contributors to social class attainment and social class mobility in the twentieth century: Both social class attainment and social mobility are influenced by pre-existing levels of mental ability (Johnson, Brett, & Deary, 2010b), which was in consistence with other studies (Nettle, 2003; Waller, 1971; Young & Gibson, 1963; Burt, 1961). So, the role of individual level mental ability in pursuit of educational attainment – professional positions require specific educational credentials. Furthermore, educational attainment contributes to social class attainment through the contribution of mental ability to educational attainment. Ever further, mental ability can contribute to social class attainment independent of actual educational attainment, as in when the educational attainment is prevented, individuals with higher mental ability manage to make use of the mental ability to work their way up on the social ladder. This study made clear that intergenerational transmission of educational attainment is one of the key ways in which social class was maintained within family, and there was also evidence that education attainment was increasing over time. Finally, the results suggest that social mobility (moving upward and downward) has increased in recent years in Britain. Which according to Burt (Burt, 1961) is important because an overall mobility of about 22% is needed to keep the distribution of intelligence relatively constant from one generation to the other within each occupational category.

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