A lot of emphasis and investment is currently being placed on “non-cognitive” factors in predicting later life outcomes. However, there has been relatively little research investigating the interplay of family background and the effects of individual differences, such as personality traits and intelligence measured in adolescence, in predicting educational attainment, annual income, and occupational prestige in adulthood. In a paper published in the Journal of Personality and Social Psychology using a nationally representative sample of 81,000 students from the Project Talent database, this is what authors Rodica Damian, Rong Su, Michael Shanahan, Ulrich Trautwein, and Brent Roberts did. They set out to address the basic issue of whether intelligence or personality traits could compensate for background disadvantage. Additionally, they wondered, could personality traits compensate for a lack of intelligence?
The authors found that both cognitive ability and personality traits are important in predicting these educational/occupational outcomes, aligned with a large body of prior research. However, they discovered that intelligence was crucial to helping students who came from disadvantaged backgrounds to catch up to their more advantaged peers, whereas personality traits had a much smaller impact. This showed in a large representative sample that the idea that things like grit (which is essentially similar to measured conscientiousness, one of the Big 5 personality traits) are more important than intelligence in predicting educational/occupational outcomes is incorrect. Intelligence is the most important factor in determining long-term achievement outcomes, and personality is unlikely to compensate for background disadvantage.
Though there is a large research literature emphasizing the importance of non-cognitive traits like personality factors, one psychologist who has been quietly yet consistently publishing a stream of research studies with his team of colleagues emphasizing both cognitive and non-cognitive factors is Brent Roberts, professor of psychology at the University of Illinois-Urbana Champaign. His work is especially important to consider because he attempts to fully account for the role of intelligence when assessing the impact of other non-cognitive factors. Using this larger body of research on intelligence, personality, and interests as an empirical starting point, his work, therefore, provides important clues as to where interventions can meaningfully have an impact and help people. I had an opportunity to ask him questions about his stream of research on this topic and where he thinks future research might be directed on untangling how cognitive and non-cognitive factors contribute to long-term achievement and life outcomes. What follows is an edited version of an interview with him.
Were personality traits or intelligence more important in predicting adulthood status attainment?
BRENT ROBERTS: We found that both cognitive ability and personality traits are important for these outcomes in particular, but that cognitive ability differences have a larger compensatory effect than individual personality traits. We were struck by the reaction of our economics colleagues who told us that the effect sizes of the personality traits (in dollars) were easily large enough to make them policy-relevant. Given the independent effects of cognitive abilities and personality traits, I'd be inclined to argue that both sets of variables are important for education and income but that cognitive abilities are more important than personality traits.
How do your findings add to our understanding of the revolution of current interest in non-cognitive traits?
In terms of the non-cognitive revolution, I think the paper reflects the truth. For most achievement-related outcomes like education, cognitive ability is always the strongest predictor. The line that non-cognitive factors do as well or better is just wrong. On the other hand, when you turn to other policy-relevant issues, like marital stability and mental health, personality is way more important. So, any broad conclusion about the relative merits of IQ and personality would be best done by being inclusive of many outcomes.
Your findings are independent of any malleability claims regarding IQ and personality, is that right?
The malleability question is an interesting one. But, yes, this paper did not include any examination of changes in either IQ or personality. Now, given the life course trajectories of both domains, it is a fair bet to make that personality change would be more actionable than IQ change, not because one is more changeable than the other, but because we typically gain in personality and decline in IQ. That said, we really need to do the longitudinal work to show that the dynamic aspect of either personality or IQ is policy relevant. My read of the IQ to "soft outcome" literature is that it is vastly overstated. I was quite disappointed when I dug into that lit for our 2007 paper.
Do you agree with the economists about policy relevance and payoff despite small personality effects?
I have little reason to argue against Heckman and the economists, but I would personally like to see more data. I don't have the expertise personally to judge what constitutes an effect size that is policy relevant. Though, once you consider the Population At Risk (PAR), which is, of course, everyone with a personality or IQ, both seem policy relevant to me.
What are your thoughts on the malleability of IQ and personality?
There was a bunch of work on the malleability of IQ done back in the 80s by the life-span folks. They could change IQ in the short run. They couldn't make it stick. We don't have an analogous literature on personality yet.
So what factors are most important from an actionable policy perspective?
I think our 2011 paper (Moffitt et al.) is about right. Death by a thousand cuts—everything has small effects. Whether that is actionable depends on your viewpoint. As a parent, nothing is probably actionable. As a society, I suspect everything is actionable if you live in a well-run place in which the populace does not expect policy changes to remake the world overnight (No Child Left Behind) and has a long view of policy. That is, nowhere but Germany.
How do your findings impact the rank ordering of people in society and related outcomes?
In terms of rank-ordering of society, an argument could be made that our goal should be to decrease the effect sizes of the individual difference variables rather than make them stronger determinants. For example, you might create education systems that rely less on cognitive power and more on skill development. If you focus simply on training people to mastery on specific skills and don't put a time limit on it, you would maximize their potential. You could also implement continuous training protocols so that people can continue to develop outside of traditional education settings—I don’t have any real optimism anything like this would work in our current political climate. Regardless, it would be fun to see a line of research that examines moderators of IDs such that certain conditions render them less important. Not many folks think that way though.
Is any of your other research (past, current, forthcoming) relevant to this discussion?
We are in the midst of several projects that are related to this discussion. First, we are investigating whether other “non-cognitive” factors help explain achievement across the life course. In particular, we have been focusing on the role of vocational interests and standard social cognitive variables, such as self-efficacy and self-concept for specific domains, like math and language. This is work with Ulrich Trautwein’s group at the University of Tübingen. Also, Rodica Damian is working on a fascinating study examining whether cognitive and non-cognitive factors might predispose you to enter into fields in which humans might eventually be replaced with robots. We are also pursuing work on the relation between educational background and attainment and patterns of development—do people born to affluence have different personalities? Does going to college affect the way your personality develops over time? These studies will emerge in the next few years.
Damian, R. I., Su. R., Shanahan, M., Trautwein, U., & Roberts, B. W. (2014). Can personality traits and intelligence compensate for background disadvantage? Predicting status attainment in adulthood. Journal of Personality and Social Psychology, 109, 473-489.
Moffitt, T. E., Arseneault, L., Belsky, D., Dickson, N., Hancox, R. J., Harrington, H., Houts, R., Poulton, R., Roberts, B. W., Ross, S., Sears, M. R., Thomson, W. M., & Caspi, A. (2011). A gradient of childhood self-control predicts health, wealth, and public safety. Proceedings of the National Academy of Sciences, 108, 2693-2698.
Roberts, B. W., Kuncel, N., Shiner, R., N., Caspi, A., & Goldberg, L. R. (2007). The power of personality: The comparative validity of personality traits, socio-economic status, and cognitive ability for predicting important life outcomes. Perspectives in Psychological Science, 2, 313-345.