Article of the Year awards 2023: Parental and family determinants of the Flynn effect

Nordic Mensa Fund awarded two article of the year- awards in 2023. Kristiina Rajaleid and Denny Vågerö from Stockholm University, Sweden were awarded for “Parental and family determinants of the Flynn effect” published in Bristol University Press.

The article contributes to the understanding of the Flynn effect, i.e. the secular rise in IQ, observed in many countries during the 20th century. Observations of the Flynn effect are mostly based on conscript data from successive male birth cohorts. Two distinct phenomena are therefore inevitably mixed: fertility differences by IQ group (‘compositional Flynn effect’), and any difference between parents and children (‘within-family Flynn effect’). Both will influence secular trends in cognitive ability.

Godfrey Thomson, as long ago as 1946, stated that ‘Actual measurement of two successive generations is desirable, indeed essential’. Such comparisons have been very rare. Rajaleid’s and Vågerös study is an exception; they explore changes in cognitive abilities between two successive generations within the same family. Potential IQ determinants and IQ outcomes in three linked generations in the Stockholm Multigenerational Study were used. School and conscript data covered logical/numerical and verbal cognitive test scores for mothers at age 13, fathers at 13 and 18, and their sons at 18. Raw (i.e non standardized) scores, and change in raw scores, were used as outcomes in linear regressions.

Rajaleid and Vågerö found that both parents’ abilities at 13 were equally important for their sons’ abilities at 18. They noted that boys from disadvantaged backgrounds caught up with other boys during adolescence. Comparing fathers with sons, there appeared to be a positive Flynn effect in logical/numeric and verbal abilities. This was larger if the father had a working-class background or many siblings. A Flynn effect was only visible in families where the father had a below average general cognitive ability at 18.

Rajaleid and Vågerö show that in the studied period there is a general improvement in logical/numeric and verbal skills from one generation to the next, primarily based on improvement in disadvantaged families. A tentative suggestion is that the first generation of children that went to preschool in large numbers benefitted from this in cognitive terms.

The general conclusion of the article seems very important: during the second half of the 20th century, the Flynn effect observed within families in Sweden is likely to represent a narrowing between social categories.