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. 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. 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. “From an evolutionary point of view, judgements of the quality of our partners must have some sort of accuracy,” says Garth Fletcher, emeritus professor of psychology at the Victoria University of Wellington, Australia. Take the case of a peacock and peahen, for example. The peahen selects their partner based on their tail – the more extravagant the better. The peahen must be accurately perceiving the quality of the tail otherwise it wouldn’t work. “It should follow that humans are very picky about their partners because we pair-bond for life. So, if we are inaccurate at assessing the quality of our partner, qualities like attractiveness or kindness wouldn’t matter so much any more.” Fletcher describes two ways that we might inaccurately assess our partners: directional bias and tracking accuracy. If you judge the attractiveness of someone as greater than their objective level of attractiveness (or greater, say, than a random person would rate them) you are said to have positive directional bias – in other words, it is as if you are wearing rose-tinted glasses. The same applies the other way if you are overly critical of someone’s level of attractiveness – and is called a negative directional bias. It is normal for people in relationships to rate their partner’s attractiveness, kindness and status as higher than others might. Where it gets slightly more complicated is when we consider the order in which we might rank those qualities, which psychologists call tracking accuracy. “Imagine I rated my partner as seven out of seven for attractiveness, six out of seven for kindness and five out of seven for status,” says Fletcher. If someone scores highly for tracking accuracy then those qualities will be in the correct order – a stranger would agree that this person was more attractive than kind, and more kind than high-status. But because of the rose-tinted glasses of positive directional bias, the stranger might actually rate them as a six for attractiveness, a five for kindness and a four for status. “People tend to be overly positive about their partner, but score very highly for tracking accuracy, which means that we must be making accurate assessments of that person’s qualities but then inflating them slightly for one reason or another,” says Fletcher. This discrepancy between directional bias and tracking accuracy might explain how our love blindness evolved. We do rank each other’s qualities accurately. If status is a priority for you, then you are likely to be attracted to people for whom status is their best attribute. How impressive you think their status is on a scale of one to seven is likely to be different to someone else’s interpretation – but that does not matter, because we all inflate the qualities of the people we love. Directional bias – consistently ranking our partner’s qualities higher than other people would –is one of the most important factors that determines how happy you are in your relationship. If you ask people what they want from a relationship, they might say that they want to be seen authentically in a way that matches their self-perceptions. But people also quite like their partner to see them as a bit better than they really are. So, when we are secure in our relationships, this manifests as being overly positive. “Your job in a relationship is to encourage your partner, to be a cheerleader,” says Fletcher. “People want their partners to see and accentuate their positives. If you want to have a good, happy relationship then it is helpful to have a charitable bias towards your partner. When you stop doing that your partner might interpret that you want them to change. It sends a powerful message that they are not good enough for you.” It is sexually advantageous to be a cheerleader for our friends, and not just our partners, too. “Women are biased about their same-sex friends,” says April Bleske-Rechek, a psychologist at the University of Wisconsin-Eau Claire. “It is well established that women compete with each other on attractiveness, but they will rate their close female friends as more attractive than them. They rate them even higher than when they rate themselves.” This could be advantageous because a group of attractive women are more likely to arouse the attention of a group of attractive men. It is beneficial to be in a group that attracts the best quality men and to be one of the more attractive women in the group. “Women should find attractive friends, but not too attractive because they get all the attention,” says Bleske-Rechek. “It’s like the idea of playing tennis with people at your level or slightly above to make you better.” What you think your partner thinks about you is also important for the wellbeing of your relationship. “This is something we are really tuned into,” says Fletcher. “We pick up on what our partner wants from us. Once you start getting into real communication problems and people develop negative bias, they start to see their partner as less attractive than they really are – then the relationship is in trouble.” While in love, people also underestimate how environmental factors (like how well they get on with the friends or family of their partner) affect their happiness. “Because their partner encapsulates their attention,” says Ty Tashiro, author of The Science of Happily Ever After, “they don’t see these environmental things that are more subtle. People only recognised environmental factors as an influence on their happiness in a relationship 5% of the time – which is a gross underestimate.” However, after a break up our love blindness is revealed. Without the physical presence of our partner, says Tashiro, we have a more objective view and are better able to see the environmental factors at play. “People are impervious to good advice from friends,” says Tashiro. “If a friend is in a bad relationship, it is very tough to communicate that to them because they are so tuned into the positives of their partner. When it is over maybe there is this window of objectivity which could be valuable going forward. At this point they might reflect and realise that there were issues in their relationship.” Fletcher warns that if you are going to commit yourself to a partner seriously, then there is good reason to acknowledge that you are also going to perceive them through rose-tinted glasses. “Romantic love is a commitment device,” he says. “Part of that is that you view your partner as better than they are. Positive bias allows us to overlook small problems and to invest in our partner once the relationship has started.” But, Fletcher says, you can’t afford to get too far away from reality. It is no good being overly positive because you will be misleading yourself about some of your partner’s flaws: “Romance is not based on objectivity, it is emotion and cognition working together or conspiring to put you in a long-term relationship.” When your friends are in seemingly unsuitable relationships, remember that they are probably seeing their partner as better than they are, and they might be impervious to your advice and unable to see better options elsewhere. Their assessment may well be wrong, but we are all guilty of it.