By Jim Stephens

You might want to think of it as the first law of domestic thermodynamics: One spouse almost always wants the room temperature to be lower than does the other one. In the vast majority of marriages, it is the man who wants the lower temperature.

Researchers who study sex differences agree that when it comes to temperature, it seems women are from Venus and men are from Planet Freon.

"This is a real phenomenon," said Kathryn Sandberg, director of the Georgetown University Center for the Study of Sex Differences in Health, Aging and Disease. "We have lots of data showing that women generally are far more sensitive to feelings of cold."

Studies among several species of mammals have shown the same results. Given a choice between two chambers on either side of their comfort range, males prefer one that is "too cold" and females one that is "too hot." And military research has shown women to be more susceptible to frostbite, hypothermia, Raynaud's disease and other cold-related conditions.

Women may prefer fans and the windows open all day. "I'm perfectly comfortable right now with just the fans," said one housewife on a steamy mid-summer afternoon. "When he walks in, he'll say, 'Oh my God, it's hot in here,' and stomp around and close all the windows and turn on the air conditioning. I know he's a miserable wretch if he's hot, so I just put on my L.L. Bean wool-lined slippers and endure it."

Some people try opening or closing air conditioning vents throughout the house to create rooms that are different temperatures. But those will limit each person to mostly a certain area. Much of the times folks just have to find a compromise.

The difference in temperature preference between men and women is explained by several factors, Sandberg said, including women's lower ratio of body mass to surface area, lesser muscle mass and a slower resting metabolism.

Further, women have a lower tolerance for cold than men. When Sandberg has had male and female volunteers hold their hands in ice water as long as possible, women are typically quicker to max out. In a survival response that researchers don't fully understand, a woman's sympathetic nervous system, which helps the body regulate its temperature, activates under cold stimulation more easily than a man's.

"If a woman likes it less cold in the house, it's probably partly due to this low tolerance to the pain of cold," Sandberg said. "Women are more sensitive to that discomfort."

Couples shouldn't despair over thermostat conflicts that might last a lifetime, said Diane Sollee, head of the Washington-based Coalition for Marriage, Family and Couples Education. In fact, because the stakes are relatively low, garden-variety thermostat disputes could even help build a strong marriage.

Happily married couples, the ones who make it all the way to the rocking chairs, argue pretty much nonstop about an average of 10 "irreconcilable differences," Sollee said. "Couples are always going to disagree about some things, always. The important thing is to talk about them with love and respect. In marriage communication, we have to teach couples to talk to each other, even when they disagree, in a way that will make them want to make love that night."

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