As a child of the 1990s, my mind turned to Chandler Bing several times while writing this article. His inability to be annoyed by Janice’s laugh in Friends is, I think, a very good analogy for the idea that we can be blinded by love. An unlikely romantic couple seeming to hit things off when all around them can see how bad a match they are is perhaps the most common trope in romantic comedies. But when people we know are unable to detect the idiosyncrasies of the people they are dating, they are not doing it for comedic effect.

It can be frustrating to see a friend in a new relationship that we think is a bad fit for them. But have you noticed that often there is little you can do to draw their attention to their partner’s flaws? Your friend could be full of praise for their new partner, which might look at best like an exaggeration and at worst like they are completely misguided.

There is a conundrum at the heart of understanding how judgements work in relationships. On the one hand, we need to accurately assess whether someone is right for us because it is such an important decision – this is someone who we might potentially spend the rest of our lives with. On the other, a lot of evidence suggests that we are very bad at evaluating the qualities of the people closest to us.

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Love blinds us to the realities of the people around us. In one study, participants in relationships were asked to write about recent romantic moments, or random events, that they had shared with their partner after being shown a photo of an attractive stranger. While writing down their story, they ticked a box every time their thoughts drifted back to the photo of the stranger. The participants who wrote about romantic anecdotes ticked the box one-sixth as often as the group who wrote about random events. It seems that we are much less likely to be distracted by attractive alternatives while concentrating on the things we love about our partner. (Read more about how accurate our first impressions are).

It makes sense that feelings of commitment will lessen our desires to look elsewhere, but love also makes us poor judges of our partners, too.

Across most cultures, there is good evidence that humans prioritise attractiveness, kindness and status (or, the access someone has to resources) when looking for a new partner. These qualities are referred to as the "Big Three". How we prefer these qualities to manifest varies across cultures, as most cultures have different standards of beauty, for example. Or when it comes to status, some people might value a particular job or level of income, while for other people a rank or social class is more important. But we can generalise to say that all humans are interested in physical attraction, how nice a person is, and whether they can provide for you. You would think, therefore, that we should be quite good at measuring these qualities – otherwise the behaviour would not have evolved in humans.