Forget atheists, secularists, and Democrats generally. If anyone s engaged in a War on Christmas, these days, it s economists. Economists, hardly known for their sentimentality, have long had a hard time wrapping their heads around the logic of presents. Joel Waldfogel, leader of the naysayers, calculated in a paper back in 1993 that Christmas presents wasted roughly $13 billion a year the gap between what the givers pay for presents and how much the recipients value the presents they re given. He s even written a book about it, Scroogenomics, out just in time for purchase as a stocking stuffer.

But are presents really as much of a waste as the poindexters would have us believe? Or do they play a slightly more complicated role in the emotional economy that can t necessarily be measured in dollars?

A recent study of how men and women react to gifts gives us at least a few hints about one of the ways we use presents: as a form of social theater to figure out who does and doesn t get us. So, as you unwrap your presents this Christmas, perhaps with a new significant other, here s hoping you haven t stepped into trouble.

In a study published in the journal Social Cognition in 2008, psychologists looked at the differences between how men and women react to bad gifts both given by a stranger and by a romantic partner. Bad gifts are particularly interesting because of the threat they might pose to a relationship. More interesting: It turned out in the study that it was actually men who were much more sensitive to bad gifts than women, and they were much more likely to take a bad gift as a signal that maybe the relationship in question wasn t going anywhere.

Gifts, as the authors point out, are viewed in the social psychology literature as markers of similarity in tastes and interests between relationship partners. And similarity at least perceived similarity has been found to reliably predict relationship satisfaction. In fact, it s been found that an inflated sense of similarity is the keystone upon which happy relationships are built. (Harsh reality is no friend of love.)

What s more, this idea of similarity being linked to compatibility and love is deeply ingrained in our culture. We ve all seen the romantic trope of a young couple falling in love over a connection to the same band or the couple who meets in a caf over reading the same book. Opposites may attract, but similarity bonds us.

In the first experiment, men and women were asked to rate the desirability of gift certificates to various stores, some appealing to most of the subjects (Barnes & Noble, for instance) and some unappealing to most (J.C. Penney). The subjects were then told they had been given a gift by their opposite-sex experiment partner (a stranger). In reality, though, the partner didn t choose the gift the experimenters did. Half the subjects got the gift certificate they rated the highest, while half were given the gift certificate they rated second to lowest. Finally, they were asked to rate how much they liked or didn t like their gift and how similar they were to the person who had supposedly chosen it for them.

In a second experiment, the same basic procedure was repeated but instead of strangers, the men and women were existing couples. And, at the end, they were asked to estimate: How much longer do you think you will date your partner? and What is the likelihood that you and your partner will get married?

In both experiments, men who had been given a bad gift rated their partners as significantly less similar to themselves. In the second experiment, with couples, the men actually rated the future of the relationship significantly more negatively. (Ouch.)

The women, however, reacted rather bizarrely to the bad gifts. In the first experiment, the bad gifts didn t change their views on their similarity to their partner at all. And in the second experiment, with their boyfriends, they actually rated them as more similar after receiving a bad gift. What s more, after a bad gift, they even had a slightly more positive outlook on the relationships future.

The authors of the study attribute this to the well-established finding that women tend to act as guardians of a relationship prone to fend off threats to the relationship and to hold more positive illusions about their mates. The increased similarity rating and the brighter view of the relationships future, thus, was a sort of overcorrection for the crappy gifts.

So, if you re a guy this Christmas (well, if you are, you re probably a guy every Christmas but you know what I mean), you re in luck. That Christmas vacuum cleaner may actually be so bad it s good. If you re a woman buying for your boyfriend, that Christmas sweater may have just set an expiration date on your couplehood.

Presents, it seems, have at least one purpose: to give us all a chance to irreparably damage our personal relationships. Happy holidays!

Ryan Sager writes the blog Neuroworld at TrueSlant.com.