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Is there a link between personality and cognitive abilities?

This new meta-analysis gets to the bottom of the question.

A new, exhaustive study published in the peer-reviewed journal Proceedings of the National Academy of Sciences reveals some striking new relationships between personality and cognitive abilities.

I’m a science journalist, and my work — which has appeared in the New York Times, Guardian, BBC, and National Geographic — is about telling stories of how the mind works. I met with the researchers behind the paper, Kevin Stanek and Deniz Ones from the University of Minnesota, and together, we plunged into the details of the connections between personality and cognitive abilities, and why they matter.

A collage created by the author Sofia Quaglia

What was the motivation behind starting this long, meticulous meta-analysis of all the research out there on how cognitive abilities and personality are linked? Why did you work more than 14 years to analyse over 1300 studies on this topic?

DO: Psychology as a science has been around for over one hundred years, and thousands of people have been toiling in the background, pumping out research studies. Few people have paid attention to the bigger picture that exists. One study at a time is great and is absolutely necessary. But scientific breakthrough and scientific understanding is only possible by pooling many studies together and looking at a panorama of what happens and that's what meta-analysis does. All of my career is a series of meta-analyses, for the most part. So, I have been on this path of using meta-analysis to answer big questions for over 30 years by now.

KS: There's a liability that people misunderstand it as just looking at personality and intelligence. What this study is about is understanding human diversity and individuality. Because we believe people don't seem to understand themselves. And if you don't understand yourself, how can you understand others? And if you don't understand others, how can you appreciate diversity? So that's what motivated us to step back: we can think more about who we are, what we want out of life, and how to get from here to there. Personality and intelligence happened to be two really core pillars of human individuality. So that's where we started.

What are the methods for pulling off such an endeavour, what did you do in your research? You pored over 1,325 studies including millions of individuals from more than 50 countries, and basically found 60,690 relations between 79 personality and 97 cognitive ability constructs.

KS: Our goal with this meta-analysis was to be the most zealous, and turn over every stone. We ended up writing letters to people, we had a research team of 30 unpaid assistants all contributing and going to libraries around the world, or having scans from librarians in different places. Having people's parents do Farsi translations for us. It was a very messy process.

DO: I feel that we need to use every piece of information that has ever been produced on a topic before we conclude anything. And I believe that science is democratic. First of all, this study was not funded by anybody. We did it. So, here's democratic point number one. Democratic point number two is the number of volunteers that were involved with different pieces of the work and how they each contributed. And then number three, are the people who actually gave us access to databases that were sitting on their computers — like militaries around the world.

When did you start seeing patterns, what was that Eureka moment like, and which patterns first emerged from your extensive analysis?

DO: We initially started with a database and Kevin ran the first iteration of our analyses all the way back in 2014. While we could see the patterns, we weren't able to decipher what they meant for a while. So, we continued looking at different ways of measuring things, finding more assessments. And then we sort of hit a breakout point of "Oh my gosh, this is what the data appear to be showing us!! I don’t mean to make it sound immodest, but it was almost like Watson and Crick sitting with the pieces of molecules trying to make up what the structure of DNA is.

When we started this, the literature told us this very loud and clear, up until two years or so ago, that cognitive ability and personality are mostly unrelated the relations between the two domains are limited. And lo and behold, in our data set we have shown that people who are industrious and who are compassionate, tend to acquire more knowledge and skills, regardless of what the domain is. I expected to find that with industriousness, but I did not expect to find it with compassion. So those were things that we have been able to show in this work.

So, being agreeable is linked with being smart?

DO: Agreeableness has two aspects to it. One is compassion and one is politeness. Compassion is positively related to all cognitive abilities. Politeness is negatively related. So why are people who are generally more polite lower in cognitive ability? There are two options that may explain the findings. One option is that being polite requires cognitive resources, knowledge about interactions and reactions of other people, and how to get along. Using that information and behaving in a polite way takes up cognitive resources. Whatever is invested in politeness is being taken away from some other area, and that's why that negative relationship might result.

KS: The other theory is that you don't have the cognitive resources, and if you don't have as high ability to deal with complexity on your own, a good strategy in life is to actually plug into a social network where you add something, but they also have some sort of insurance. We're currently not sure which way it goes. That's probably something for longitudinal studies to tease out. But it's interesting to consider those options.

Can we dive a little bit deeper into what some of those assumptions that you've been able to overturn are and the main findings that you find most interesting, most exciting, and most revealing?

DO: Most people were aware, from prior research, that "test anxiety" relates negatively to cognitive performance on tests. That was a well-established finding. What wasn't well established is that we find just as high correlations with depression. We found that people experiencing depression tend to score poorly on cognitive ability tests, regardless of which type of cognitive ability we're talking about. The same goes for anxiety and suspiciousness, other facets of neuroticism. People previously thought tests were making people anxious and causing them to perform poorly on cognitive tests too. Now we're saying "No! The issue is bigger." Anybody who's depressed and who is anxious and who is suspicious will tend to have a lower level of cognitive ability. And you can ask, which comes first? Cognitive ability or anxiety and depression? There are theories that would support the primacy of one over the other. But nonetheless, those connections are more fundamental than just test anxiety. So that's one.

KS: Within the Big Five personality traits — extraversion, agreeableness, openness, conscientiousness, and neuroticism — extraversion breaks into enthusiasm and assertiveness, and within those, there are facets, and "activity" is one of those. Active people are high energy, and there are people who seem to have boundless energy and bustle. It was interesting to note that those people just tended to, on average, have higher cognitive ability scores. They tend to be better at retrieving things from their memory. And they're really efficient in information processing. This was in contrast to the stereotype of the intellectual person who's in the library all the time or closeted away in their room. That's not what we found. Definitely not what I had expected going in and definitely not what the popular stereotype is.

What are the implications of carrying out research like this? What can real people do with this knowledge about their personalities and cognitive abilities?

KS: We can't turn a blind eye: there are real differences between people. And if we can understand them better, I think it would go a very long way toward actually appreciating them more. We also provide evidence in the paper that these traits do tend to change over time. I think what's difficult is consciously changing these traits. So certainly, these things change with age. For example, a three-year-old is not as smart as a 24-year-old. And those things develop and have their own natural curves and trajectories but what's harder is saying, "I want to be more open-minded." We don't have a lot of proven interventions that can change that in an enduring way. There are interesting things like religion, the military, and significant life events that seem to have an impact, but I haven't seen literature that shows true intervention effects.

DO: The only trait that seems to be more malleable with direct intervention is neuroticism. You can have depressed folks seek treatment and it improves their depression levels. The upshot of that is that we showed that depression is negatively correlated with cognitive abilities. Depressed people's minds tend to shut down in terms of cognitive performance. By interventions into neuroticism, we can potentially also increase people's cognitive performance. There's at least one domain that we know that we can do something with.

Off the top of my head, I can come up with quite a few nefarious uses for this sort of data. Doesn’t this risk prematurely labelling people as something or the other?

DO: All personality traits are very fine refinements along a big continuum. All of us are incredibly unique individuals. It is impossible to categorise people into buckets. You can't bucket anybody into a single area. Simply, we can now use additional research from psychology to say: if your goal is to become a negotiator, which skills, which knowledge, and which cognitive abilities will you draw on? And how easy or more difficult will it be for you? Do you have the industriousness to bring you up to par if you don't have the skills? By using these multiple dimensions of personality and cognitive ability, it reduces the likelihood that anybody can be pigeonholed into anything.

KS: You mention sorting people being nefarious, but I would actually say it's one of the biggest missed opportunities that exist. There are 8 billion people in the world: how many marriages are the optimal couple? There are millions of jobs in the world: how many people are in the optimal job for them? There's an almost infinite number of places you could live in the world: how many people are living in the place that's actually best for them? There are too many choices for us to go out and find out on our own and just experience. It's too hard to know ourselves well enough and know the options well enough, to find those matches. So, I see the optimistic side of it, where if we can understand ourselves better and we can come up with much, much better matches, which ultimately means people are happier, healthier, and more productive.

Is the way we’re living right now that bad?

KS: People can be given information about themselves and about others, and understand others better so that they can make more optimal choices for themselves. It increases personal choice and does so using a much higher number of personality and cognitive ability dimensions than ever before thought. The alternative, if you don't do that, is convenience: who's nearby is much more likely to become your mate than the ideal person. It's also biased: certain groups get chosen more for certain things because of preconceived bias. And it's also marketing. It's what other people want for you, brands marketing to you, or people pushing you and influencing you even without your knowledge. Because you don't know yourself well enough to have a compass.

Ok, so where do we go from here?

DO: In psychology, behavioural economics, medicine, and education, people study or include in their studies either a personality variable or a cognitive ability variable — but it is included by itself. Maybe you get the big five, maybe you get general intelligence. Maybe you get memory. What our study very clearly shows is, if you think that conscientiousness is responsible for an effect, you'd better include the cognitive abilities that conscientiousness is correlated with. You cannot just include conscientiousness and say, "I discovered conscientiousness does x and y," you have to make sure that you have included what conscientiousness is connected with.

From a practical point of view, applications can be put together. For example, if we know the characteristics of students, how can we tailor educational programs to better suit their personality and ability constellation? People have tried it with cognitive ability alone, but not the two of them put together. How can we refine the recruitment and selection systems of companies? We think that we are selecting for compassion when we select nurses, well, guess what it's going to bring other traits along with it in terms of skills and capabilities. From a clinical point of view, we can enhance therapeutic interventions in clinical settings. The implications of this research are vast in terms of the domains that it touches.

KS: The biggest threat to humanity is not predators, disease, or even conflict. It's ignorance. So the point of this research was to illuminate further some of the truths around us, so that we can lead better lives. It's really about continuing to push people to better understand themselves.


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