Why my mom didn't buy me a slot car track for Christmas in 1978, even though I told her that's what I wanted

[This article was originally posted in December, 2006]

I'm not bitter about this, honest I'm not, but it does often seem that people who know you very well end up buying really lousy gifts. What I really want to find out is this: why do they do that? It turns out, market researchers want to know, too. How can they have a prayer of selling people things they don't want when people can't even convince their loved ones to buy them things they do want?

Davy Lerouge and Luk Warlop have designed a clever study to examine this very issue. They wanted to know whether couples who've been together for at least six months were any better at predicting each other's preferences than they were predicting preferences for strangers. They decided to study furniture preferences, because it's something couples generally have to agree on together. Also, since people don't buy furniture very often, most couples probably wouldn't have a specific purchase to use as a reference, and instead would be relying on general knowledge of each others' preferences.

Lerouge and Warlop recruited 35 couples to participate in the study. Each partner was placed in a separate cubicle for the duration of the study, and had no contact with his or her mate. They then were shown pictures of 30 different sets of bedroom furniture and asked to indicate their impression of it (positive or negative). The next part was the key to the study:

Each partner was shown 30 new furniture sets -- the sets the other partner had already rated. In each case, they were asked to predict how another person would feel about the furniture. Half the participants were told they were predicting their own partner's preference, and the other half were led to believe they were choosing for a stranger. In fact, all participants were predicting their own partner's preferences. After each prediction, the partner's actual preference was revealed, so as the study progressed, presumably each participant would better understand his or her partner's preference, and gradually make better predictions. Here are the results:

Overall, participants were better at predicting their partners' tastes when they believed they were predicting the tastes of a stranger. When they knew they were predicting their own partners' tastes, the accuracy of predictions depended on how similar their own tastes were to that of their partners.

Here's the key finding: When partners' tastes were different from their own, then they were better at predicting each others' tastes if they believed they were predicting the tastes of a stranger. So, if your partner has different tastes from you, then even if you learn exactly what their tastes are, that information doesn't help you make predictions about their tastes. Instead, you substitute your own tastes.

When you know someone well, it appears, you begin to assume they have the same tastes as you do. If you really do have the same tastes, this works out fine, but if your tastes are different, then you can't count on your partner to figure that out -- even if you tell them. Two subsequent experiments, with even more furniture photos and more opportunity to learn partners' preferences, confirmed these results.

Lerouge, D., & Warlop, L. (2006). Why is it so hard to predict our partner's product preferences: The effect of target familiarity on prediction accuracy. Journal of Consumer Research, 33, 393-402