BASEL, Switzerland — Long-lasting marriages may thrive on love, compromise and increasing ignorance about one another. Couples married for an average of 40 years know less about one another’s food, movie and kitchen-design preferences than do partners who have been married or in committed relationships for a year or two, a new study finds.

Two University of Basel psychologists, Benjamin Scheibehenne and Jutta Mata, working with psychologist Peter Todd of Indiana University in Bloomington, observed this counterintuitive pattern in 38 young couples aged 19 to 32, and 20 older couples aged 62 to 78. The greatest gap in partner knowledge was in predicting food preferences, an area with particular relevance to daily life, the scientists report in a paper scheduled to appear in the Journal of Consumer Psychology.

“That wasn’t what we expected to find, but this evidence lends support to a hypothesis that accuracy in predicting each other’s preferences decreases over the course of a relationship despite greater time and opportunity to learn about each other’s likes and dislikes,” Todd said October 13 during a visit to the University of Basel.

Older couples’ knowledge decline partly reflects a tendency by partners to pay increasingly less attention to one another, because they view their relationship as firmly committed or assume that they have little left to learn about each other, the researchers propose. Consistent with that hypothesis, long-term partners in the new study expressed more overconfidence in their knowledge about each others’ preferences than people in short relationships did.

In long relationships, partners may also come to perceive an unduly large amount of similarity between themselves, the scientists add. Members of long-term relationships often attributed their own food, movie and design preferences to partners who had different opinions.

If the new finding holds up, reasons for a declining ability to predict a partner’s preferences over time would require closer study, comments University of Basel psychologist Ralph Hertwig, who was not involved in the research. In the case of food, taste perception suffers as people get older, Hertwig notes, which could make it more difficult for long-term partners to keep track of each others’ increasingly inconsistent food likes and dislikes.

It’s also possible that older couples in the new study come from a generation in which men and women generally knew less about each other to begin with than couples do today, Hertwig says.

What’s more, long-term partners may be especially apt to tell “white lies” to each other in order to keep the relationship running smoothly, thus diluting their knowledge of one another.

Participants in the new study, who were recruited in Berlin, rated their own and their partners’ preferences on a four-point scale, from “don’t like it at all” to “like it very much.” Judgments were made about 40 food dishes taken from a website that displays cooking recipes and images of finished dishes, 40 movies taken from offerings on a website that sells movies not shown in theaters but available on DVD, and 38 kitchen designs chosen from online furniture catalogues.

On average, members of younger couples accurately predicted a partner’s food preference 47 percent of the time, versus 40 percent for members of older couples. A comparable disparity emerged for movies and kitchen designs, but accuracy was slightly lower for everyone making those predictions.

Despite their relative disadvantage in predicting partners’ preferences, long-term couples reported more satisfaction with their relationships than did younger couples.

Image: Flickr/Josh Liba

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