What's your favorite theory in psychology

"Love is like fever," sighed the novelist Stendhal. "It arises and goes out without the will having the slightest part in it ..." The American psychologist David Lykken remembered this complaint when he and his colleague Auke Tellegen tracked the flight of Cupid's arrows: Why does a man make a decision for the one, a woman for the one? Are there any rules by which they vote? Or do they fall in love at the right moment with the next best person who comes along, as if under the spell of the magic herb from the midsummer night's dream? The results of Lykken's new large study speak in favor of the magical variant and thus shake many theories of psychologists who prefer clear laws.

A uniform doctrine had just prevailed in the faculties: We like those who resemble ourselves - we like to join people like us. The counter-thesis, according to which opposites attract, has been refuted by numerous research results. According to the textbooks, married people are similar in intelligence, religious affiliation, education, height, eye color and the like. At first glance, the new study published in the Journal of Personality and Social Psychology comes to the same conclusion. 3392 spouses completed personality tests, provided information about their interests and hobbies, and expressed their opinions on controversial topics. Again the married couple looked alike. But the similarities were more of statistical interest, they were only weak. A 300-question personality test confirmed that both of them were mostly only distantly related character traits. The man often dared to have different skills than the woman. In their spare time, they only did the same occasionally. What the spouses really had in common, apart from the duration of their training, was their attitude towards traditional values. When it came to abortion, defense of the homeland, or nightclubs, there was broad agreement. Religious activities achieved the highest value. The typical couple goes to church together - or they stay at home in peace. The researchers classified the subjects on a total of 88 scales, but only on ten did the married people achieve at least somewhat comparable values. When Lykken took a closer look at earlier studies, he found that they, too, had shown statistically significant, but ultimately only moderate, similarities - there, too, religiosity and conservative worldview still united the couples most. With so little agreement it cannot be explained that those willing to marry ever find each other.

Another favorite theory of psychologists is also poorly compatible with the results of the new study. Its proponents see the marriage market as exactly what the word suggests: a market economy event. This everyone-gets-what-he-deserves model (just deserts model), which fits in with the times but is already decades old, postulates that men and women first assess their own value in this market. Then they try not to sell themselves under, but also not to make too high demands. "Sell if you can, you are not suitable for all markets", this strategy coolly formulated by the philosopher William Shakespeare. The game of supply and demand ultimately leads to connections between participants with a comparable market value. According to this theory, Lykken should have found similar partners.

It probably only surprises experts when such unromantic explanations of great feelings fail. Most others see the miracle of love precisely in the fact that it cannot be explained so easily, especially not with the laws of the bazaar. Doesn't everyone have personal likes and dislikes that determine who he or she loves? According to this logic, a separate theory of partner choice should be established for every man and woman. Any number of different inclinations could be combined in each one. There would be rules, but in each case their own, so that it would seem that blind chance would rule. How could science ever verify this thesis?

Because of this difficulty, Lykken chose a group of people for his investigation that researchers have often rescued from seemingly hopeless situations: twins. They grew up at the same time and mostly in the same environment, and identical genes also have the same genetic make-up. It has been shown again and again how much they are alike. If there are rules, no matter how individual and complicated, then twin brothers would have to choose women who have at least a few things in common. But despite their extensive test battery and the collection of questionnaires, the scientists did not find such similarities. The partners of a pair of twins are hardly more similar to each other than the computer calculated for purely randomly combined pairings.

The same result is obtained without computer statistics. The scientists asked each twin how they found the chosen one of their doppelganger when they first saw her. Could he have fallen in love with her himself? Not at all. Almost every second person didn't even find her likeable. On the other hand, when it came to - heartless comparison - clothing, furniture or vacation destinations, they had almost the same taste. Female twins fared no differently with their sisters' husbands.

Conversely, the spouses of one twin denied that they could do much with the other twin. Just 13 percent of men said they could have opted for their wife's twin sister. Are you suppressing feelings for your twin's wife? Not to be ruled out, but unlikely in the light of the other results, says Lykken.

These findings are a hard blow to many love theorists. He also meets psychoanalysts who are convinced that the personality of the parents determines the choice of partner for the children. Twins have the same parents. Lykken comes to a provocative conclusion: people "almost by chance" fall in love with each other and that's a good thing. Because only in this way could humanity survive. Our ancestors in the Pleistocene lived in small groups, the choice was minimal. But it was extremely important that the parents of a child stay together. Because human infants are extraordinarily helpless beings, the mother alone could hardly raise them. So humans became the only primates other than gibbons to form pairs. Blind love is the bond that holds it together. She doesn't care about any law, just as Carmen Don José announced at their first meeting and soon proves.

In the next step, too, biological theory follows the plot of the opera. Romantic love doesn't last forever. After three or four years, experts claim to have found out, even the biochemistry of the brain changes and the stormy feelings associated with it pass. At least the first child is now out of the woods. At the end of this period, separations accumulate in most cultures.

But many couples stay together. The love has tied them together "until the glue holds", as Lykken puts it. In the time of passion, comradely love has grown and it continues. The partners have adapted to each other and got used to each other, they now share many common experiences. These bonds are strong, but they take time to solidify.

The theory of love, which is being blessed by science, is of course not entirely new. Many cultures rely on the fact that a harmonious relationship will be established, if only it is ensured that a young man and a young woman stay together for a few years. The institution of marriage was invented for this purpose. A long-term study compared the marital happiness of Japanese married couples in relationships arranged by their parents with that of American couples who, at least by their own account, married out of love. In the beginning, the American spouses interviewed were much more in love than the Japanese. But ten years later this difference no longer existed, because the love of American couples had waned more than that of Japanese. Yet, here as there, many were quite satisfied with their marriages.

With arranged marriages going out of fashion in the West, a problem remains in the end. Even if personality doesn't seem to play a big role when choosing a partner, lovers have to somehow decide for each other. The most important known factor is how long and how well they have known each other. The comforting psychology textbook by Rita Atkinson and co-authors formulates the lesson from many studies as follows: "If you are not beautiful or your admiration is not returned, be persistent and hold on. Proximity and familiarity are your most powerful weapons."

Perhaps at some point psychology will find even more rules according to which people fall in love. Until then, Blaise Pascal remains undeniable. The most famous sentence of the philosopher is the motto of Lykken's study: "The heart has reasons that reason does not know."

Jochen Paulus

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