The personality–intelligence interface: insights from an ageing cohort

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Abstract

Recent attempts have been made to provide a theoretical model that accounts for the findings linking intelligence and personality, and it has been suggested longitudinal research is necessary to empirically evaluate this (Chamorro-Premuzic & Furnham, 2004). The current study uses longitudinally collected data on almost 500 people to investigate the link between intelligence (assessed in the same individuals at ages 11 and 79) and the non-cognitive traits of typical intellectual engagement (TIE) and Big-Five personality (measured in late adulthood). Intelligence in childhood and late adulthood was significantly related to the personality factors Emotional Stability and Intellect (r = 0.11–0.32, p < 0.05). When initial ability (age-11 IQ) was controlled for, the association of age-79 IQ and Intellect fell to almost zero (r = 0.02, ns), whereas the significant Emotional Stability correlation was largely unaffected. TIE associated with IQ at both ages (age-11 r = 0.21 and age-79 r = 0.13, p < 0.01); however, controlling for prior ability removed the TIE and age 79-IQ association (r = −0.01, ns). Structural equation modelling of these data suggested no direct link between contemporaneous Intellect, TIE and late adulthood ability, indicating that they are related through the lifelong stable trait of intelligence.

Introduction

The scientific study of individual differences primarily focuses on the explanation, prediction and consequences of intelligence and personality. Whilst the links observed in empirical studies between personality and intelligence have recently come under increasing scrutiny, it has been argued that a theoretical model for this interface is lacking (Chamorro-Premuzic & Furnham, 2004). To address this issue, Chamorro-Premuzic and Furnham postulated a model to account for the links observed which, they suggested, should be tested empirically and preferably longitudinally. The present study is a first step in this endeavour, as it makes use of longitudinally collected mental ability scores (recorded at ages 11 and 79 in the same individuals), typical intellectual engagement, and personality, assessed in a healthy, ageing cohort. The results have implications for the understanding of some aspects of the personality–intelligence interface.

Section snippets

The personality–intelligence interface

In order to explain the mechanism underlying the observed links between ability and non-ability individual differences, it is first necessary to have a consensus regarding the measurement and conceptualisation of these constructs. Within the domains of personality and intelligence research, this has been achieved to a sufficient degree to allow an examination of the interface. An individual’s personality can be broadly described by scores on five higher order factors, often referred to as the

The present research

The current study assesses personality in a healthy, elderly cohort of individuals (the Lothian Birth Cohort 1921), and examines its relationships with intellectual function. Data on life-long cognitive traits have been collected in this cohort which allows an examination of the cognition-TIE-Intellect relationships; these can only be tested longitudinally. Mental ability was assessed using the same test delivered at ages 11 and 79. Personality and typical intellectual engagement were assessed

Participants

The recruitment of the Lothian Birth Cohort 1921 (LBC1921) has been described extensively elsewhere (Deary, Whiteman, Starr, Whalley, & Fox, 2004). In summary, the members of the cohort sat a test of mental ability (the Moray House Test: MHT) at school on June 1st 1932 when aged between 10.5 and 11.5 years old, as part of the Scottish Mental Survey of 1932 (an assessment of almost every Scottish schoolchild born in 1921). The MHT consists of 71 items, with a maximum score of 76. It was

IQ and personality

In order to examine the associations between mental ability and personality, the 5 factors of personality were scored as instructed (Goldberg, 2001). The correlation coefficients with age-11 and age-79 IQ are shown in Table 1. Significant associations to age-11 and age-79 IQ are seen with Emotional Stability (r = 0.11, p < 0.05 and r = 0.21, p < 0.01 respectively) and Intellect (r = 0.32 and 0.22, respectively, both p < 0.01). These results suggest that those individuals with higher IQs (at ages 11 and 79)

Discussion

Early-life ability was related to the personality factors of Emotional Stability and Intellect. A similar pattern of associations was observed with later ability, although controlling for early ability removed the association with Intellect. The first unrotated component from the TIE scale was found to have greater associations with the personality factors than with the ability measures. This TIE factor was also related to IQ at ages 11 and 79, although again, controlling for prior ability

Limitations of the current study

In relation to the findings reported here, the limitations fall into three areas. Firstly, these are related to the measures used in assessing the various constructs; secondly, longitudinal studies suffer from attrition and this study is no exception; and thirdly, the temporal ordering of the assessments was not ideal.

The current analysis used the IPIP to measure personality instead of the more commonly used NEO inventories. However, this measure has recently been validated against the NEO-FFI,

Conclusions

The interface between personality and intelligence is clearly an important area requiring thorough investigation as it has been suggested that non-ability factors may have an important role to play in the development of intellectual abilities. The current study has taken the first steps in examining the model presented by Chamorro-Premuzic and Furnham (2004) in a longitudinal and empirical manner. The most novel finding was that once initial ability was controlled for, the associations of

Acknowledgements

Alan Gow holds a Royal Society of Edinburgh/Lloyds TSB Foundation for Scotland Studentship. Ian Deary is the recipient of a Royal Society-Wolfson Research Merit Award. The phases of the LBC 1921 Study reported here were funded by the BBSRC and the Scottish Executive Health Department Chief Scientist Office. The personality–IQ associations were presented at the 12th European Conference on Personality, Groningen, the Netherlands, July 18–22, 2004.

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