Falling in Love With Someone You Shouldn’t

“The heart wants what it wants—or else it does not care.”

Written by the poet Emily Dickinson in the spring of 1862, these words have been quoted countless times in this or similar forms. Mostly, they are used whenever someone tries to explain why he or she fell in love with someone they really shouldn’t, like the partner of a good friend or sibling.

They are, of course, completely wrong.

Like all human behavior, love and affection are caused by the brain, with the heart doing hardly anything in this context. So, in order to understand why we sometimes fall in love with people who we really shouldn't, learning about the neuroscience of love can be helpful.

You might think that something as magical and inexplicable as love might be beyond the scope of modern brain research. However, it is surprising how much neuroscientific research on human affection and love has been published over the years.

Love is a highly complex and heterogenous feeling and as such, a multitude of brain regions are involved in it. However, some brain regions are more relevant than others. In a recent article on the neuroscience of human attachment, researcher Ruth Feldman suggested a new model for the neuroscience of love (Feldman, 2017). This model assumes that the intensity of love and the quality of attachment is guided by the neurotransmitter dopamine in one specific brain region, the so-called nucleus accumbens. The nucleus accumbens is a brain area that is involved in reward-seeking behavior.

So what does dopamine do?

Dopamine is a neurotransmitter that is involved in generating behavior that leads to something rewarding. A reward can be a lot of things, like money, food, social interaction, and everything else people enjoy. In the context of love, it can be something as small as a smile from the person we love to a kiss or a honeymoon. However, there is something tricky about dopamine: It functions as a reward prediction error signal. This means a larger reward does not necessarily lead to a higher dopamine release. What is important is how unexpected the reward is. Let me give you an example. If you expect a nice new cookbook for Christmas and get a car instead, there is a high reward that is also highly unexpected — dopamine levels in the nucleus accumbens will be high. However, if you expect a car and get a car, the dopamine release will be lower. That means that the more you expect a reward, the less the positive reaction will be.

What does this have to do with falling in love with someone you shouldn’t?

The danger of dopamine is that if we are in a committed long-term relationship, we get to know our partners better and better. At some point, rarely anything unexpected will ever happen, as we know pretty much everything about how our partner looks, feels, and acts. However, high dopamine release will only happen if something unexpected happens, leading to a decrease of love over time in many relationships.

Now think about what will happen if you fall in love with someone who is completely out of reach, like a married person. In this context, it is unlikely that you ever get to know the person extremely well. Here, even a simple smile or a slight touch can be perceived as extremely rewarding because it is so unexpected — an intense feeling of love can result. As the person is unlikely to spend a lot of time with you, the relationship never enters a phase in which high rewards are expected, so whenever something positive happens, the intense feeling of love persists. This way, someone can be in love with somebody completely out of reach over long periods of time, even years.

Taken together, falling in love with someone you shouldn't is not some mysterious magical process beyond the understanding of the human mind. It may simply be a function of how reward works in the human brain — nothing more. This suggests that surprising each other is vital to keeping the fire alive in long-term relationships. If something unexpected happens from time to time, an intense feeling of love will persist and the danger that one partner falls in love with somebody else will be lower.

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