By guest blogger David Robson

It’s now well known that many of us over-estimate our own brainpower. In one study, more than 90 per cent of US college professors famously claimed to be better than average at teaching, for instance – which would be highly unlikely. Our egos blind us to our own flaws.

But do we have an even more inflated view of our nearest and dearest? It seems we do – that’s the conclusion of a new paper published in Intelligence journal, which has shown that we consistently view our romantic partners as being much smarter than they really are.

The researchers, Gilles Gignac at the University of Western Australia and Marcin Zajenkowski at the University of Warsaw, also tested whether the couples’ actual IQs influenced their relationship satisfaction – with surprising results.

There had been some previous signs that we are especially optimistic about our loved ones’ attributes. When it comes to physical attractiveness, for instance, we tend to think that we have managed to attract someone who is even hotter than us – an effect sometimes called the “love is blind bias”. But past studies had failed to find a similar optimism for estimates of partners’ intelligence. Overall, people seemed to judge their partners’ intelligence as equal to their own – rather than thinking that they were especially clever.

For the new study, the researchers recruited 218 heterosexual couples, who had been together for an average of six years, and around a quarter were married. Rather that guessing IQ scores – which might be confusing for participants who have little knowledge of IQ tests and their scoring – the participants had to estimate their own intelligence and their partner’s intelligence using a more intuitive, graphical scale (see below). The researchers then converted those estimates to IQ points according to the known statistical distribution of intelligence – the famous bell curve. To find the participants’ actual, objective IQ scores, the researchers also asked them to take a standard test of non-verbal intelligence known as the Raven’s Advanced Progressive Matrices.

As the previous research on individual overconfidence had found, most participants over-estimated their own intelligence by a huge margin – the equivalent of around 30 IQ points on average. Overall, only 0.9 per cent of women and 1.8 per cent of men assessed their own intelligence as being below average (even though 68.8 per cent of the women and 55.0 per cent of the men in this study scored below 100 – the mean IQ of the population as a whole).

The participants’ estimates of their partners’ intelligence were even more skewed. The men thought their wives and girlfriends’ IQs were around 36 points higher than they really were; the women thought their husbands and boyfriends’ IQs were 38 points higher than the reality. In other words, if you are like the majority of people in this sample, your partner is probably much less clever than you believe.

Besides this eye-catching result, Gignac and Zajenkowski’s paper is rich with other findings. They were interested, for instance, in whether people tend to hook up with someone of similar cognitive ability – and whether that “intellectual compatibility” is important for their happiness together. As previous research has found, there was a moderate correlation between the partners’ actual IQ scores – so in general people do seem to pick partners who roughly match their intelligence.

Maybe we have a slight preference for people with similar smarts to ourselves, or maybe it’s due to the fact that we have more opportunity to get romantically involved with people of roughly similar intelligence – in education or at work. Whatever the reasons, the degree of similarity of couples’ IQs didn’t seem to influence their relationship satisfaction – overall, couples with lower “intellectual compatibility” appeared to be just as happy as the couples who were more closely matched.

Gignac and Zajenkowski also examined whether the men or the women in their sample were better at estimating their partners’ intelligence. According to some evolutionary psychologists, because the responsibility of pregnancy, childbirth, and usually childrearing, falls more directly on women, they should be pickier than men about the kind of person they choose to reproduce with. If true, it would make sense for women to have evolved to be more perceptive than men of differences in other people’s intelligence. Yet the researchers found no evidence of this.

As the researchers admit, there are some limitations to their study. They only used a non-verbal IQ test, for instance, and it’s possible you would see different results if you also looked at verbal questions. After all, the size of someone’s vocabulary and their linguistic fluency may be easier for a partner to judge accurately.

But overall, the findings help extend our understanding of our self-serving biases, showing our egotism and self-confidence can sometimes spill-over to our loved ones. Maybe we like to think we’re with a partner who reflects an even better version of ourselves.

—People tend to overestimate their romantic partner’s intelligence even more than their own

Post written by David Robson (@d_a_robson) for the BPS Research Digest. David is the author of The Intelligence Trap, published in the UK and commonwealth by Hodder & Stoughton on 7 March. It is available for pre-order now.