And now for some helpful scientific advice: When that IRS agent comes to your office to conduct an audit, offer him a cup of coffee. And when you're sitting down to do your holiday shopping online, make sure you're cradling a large glass of iced tea. The physical sensation of warmth encourages emotional warmth, while a chilly drink in hand serves as a brake on rash decisions — those are the practical lesson being drawn from recent research by two Yale-educated psychologists, published last week in Science magazine.

Encountering warmth or cold lights up the insula — a walnut-sized section of the brain — says John A. Bargh, a professor of psychology at Yale, who co-authored the paper with Lawrence E. Williams of the University of Colorado who received his Ph.D. from Yale earlier this year. And the insula is the same part of the brain engaged when we evaluate who we can trust in economic transactions, Bargh says.

Psychologists have known since the mid 1940s that one person's perceptions of another's "warmth" is a powerful determining factor in social relationships. Judging someone to be either "warm" or "cold" is a primary consideration, even trumping evidence that a "cold" person may be more competent. Much of this is rooted in very early childhood experiences, Bargh argues, when infants' conceptual sense of the world around them is shaped by physical sensations, particularly warmth and coldness. Classic studies by Harry Harlow, published in 1958, showed monkeys preferred to stay close to a cloth surrogate mother rather than one made of wire, even when the wire "mother" carried a food bottle. Harlow's work and subsequent studies have led psychologists to stress the need for warm physical contact from caregivers to help young children grow into healthy adults with normal social skills.

Feelings of "warmth" and "coolness" in social judgments appears to be universal. Although no comprehensive worldwide study has been done, Bargh says that describing people as "warm" or "cold" is common to many cultures, and studies have found those perceptions influence judgment in dozens of countries. To test the relationship between physical and psychological warmth, the researchers conducted two experiments. The first involved a group of 41 undergraduates who were taken by elevator to a fourth floor room. During the ride, a research assistant who was unaware of the study's hypotheses, handed the test subject either a hot cup of coffee, or a cold drink, to hold while the researcher filled out a short information form on a clipboard. The drink was then handed back. When the subjects arrived at the testing room, they were presented with a personality profile describing "Person A" and asked to rate that person's personality traits. Those who had briefly held the warm drink assessed Person A as warmer than test subjects who had held the iced drink.

"We are grounded in our physical experiences even when we think abstractly," says Bargh.

In a second experiment, done under the guise of a product-evaluation test, participants were asked to hold heated or frozen packs used to treat muscle aches. They were then told they could receive a gift certificate for a friend, or a gift for themselves. Those who held the hot pack proved to be more likely to ask for the gift certificate for a friend, while those who held the frozen pack tended to keep the gift.

"It appears that the effect of physical temperature is not just on how we see others, it affects our own behavior as well," Bargh said. "Physical warmth can make us see others as warmer people, but also cause us to be warmer — more generous and trusting — as well."

The practical advice Bargh takes away from the study is that important decisions are best taken with a cold drink in hand, because that part of the brain that triggers caution in economic and trust decisions is stimulated by cold sensation. Conversely, if you are planning on introducing your fiancee to mom and dad, pass on the icy martinis in that air-conditioned, glass and steel restaurant; do it over a mug of hot chocolate in front of a roaring fire.