Language development and intelligence in midlife

Abstract

Individual differences in early language skills have been found to be associated with other cognitive outcomes in childhood and adolescence. However, research is limited on whether these associations persist into adulthood. In this study, we examined potential associations of the timing of early language milestones with cognitive ability in a prospective cohort study of 938 singletons from the Copenhagen Perinatal Cohort (CPC), who participated in a 50‐year follow‐up examination in 2009–2011. Later attainment of a number of milestones was associated with lower midlife IQ with the strongest associations found for ‘Naming objects/animals in pictures’, ‘Forming a sentence’, and ‘Sharing experiences’. Milestones related to language explained 6.7% of the variance in midlife IQ, while milestones related to social interaction explained 3.1%. The study provides evidence that individual differences in language development during the first years of life are associated with intelligence in midlife. What is already known on this subject? Differences in early language skills are associated with other cognitive skills in childhood and adolescence. No study has examined this association from childhood through midlife in a large community‐based sample. What does this study add? Early language development is associated with intelligence in midlife. A total of 6.7% of the variance in midlife IQ is explained by milestones related to language. Adjustment for potentially confounding factors did not change the associations.

A potential link between early language developmental milestones and personality traits in adulthood

“…To the best of our knowledge, this is the first study to investigate associations between the timing of early language development and personality in midlife. However, a previous study based on the same birth cohort found significant associations between faster language development and intelligence in midlife (Flensborg-Madsen & Mortensen, 2018c), which may support our results on associations between language development and openness to experience as high correlations are often found between intelligence and openness (Matthews, Deary, & Whiteman, 2009).…”

“…All variables were included as linear continuous variables except for parity (included as a binary variable indicating first or later pregnancy), smoking (included as a binary yes/no variable), and sex. Additionally, we included intelligence as a covariate in supplementary analyses (Online Supplemental Tables S1 and S2) as intelligence has been found to be associated with both language milestones (Flensborg-Madsen & Mortensen, 2018a, 2018b, 2018c) and personality (Flensborg-Madsen & Mortensen, 2014). Assessments of intelligence were based on Wechsler’s Adult Intelligence Scale (Wechsler, 1958) at the PDP follow-up and the Intelligenz-Struktur-Test 2000 R (Amthauer, Brocke, Liepman, & Beauducel, 2001) at the CAMB follow-up.…”

“…The specific timing of attainment of language has been the focus of several studies linking language development to other aspects of life related to emotional, social, and cognitive development (Conti-Ramsden & Durkin, 2012; Petersen et al, 2013; Tõugu & Tulviste, 2017; Walker, Greenwood, Hart, & Carta, 1994). The majority of these studies have focused especially on the relationship between language and cognitive development, and significant associations between the two aspects of development have been suggested (Abt, Adler, & Bartelme, 1929; Flensborg-Madsen & Mortensen, 2018b, 2018c; Liao et al, 2015).…”

“…As language is an important aspect of social interaction, we expect individuals who attain language milestones relatively fast to be more extraverted. Additionally, as language development has been found to be significantly associated with intelligence (Flensborg-Madsen & Mortensen, 2018a, 2018b, 2018c), faster language development may also be associated with the personality trait of openness to experience. Finally, it can be hypothesized that individuals who attain language milestones relatively late will be higher on neuroticism in adulthood which may reflect recurring mutual interactions between language development and neuroticism.…”

Predictors of early life milestones: Results from the Copenhagen Perinatal Cohort

“…Parental social status is in this study defined as a joint measure of both educational and occupational aspects as well as the character of the living accommodation, and the results are therefore in accordance with previous studies showing that socioeconomic status [23] and maternal education [24–26] are positively associated with language development, in particular since we observed the strongest association for milestones related to Language. Cognitive and language development are closely related, and in the Copenhagen Perinatal Cohort (CPC), language milestones predict young adult and midlife intelligence [16, 45]. Since the CPC measure of parental social status is a strong predictor of offspring adult intelligence [46], a relatively strong association between parental social status and Language milestones was expected, but the strength of the association was considerably weaker than the association between sex and Language milestones.…”