A friend asked me for a quick tip from BLONDES that she could use for her date that evening. I threw out a few ideas — home-cooked-meal smells may be aphrodisiacs, for instance. But this was a first date, she said, and she wanted to be cool and casual. She had in mind a wine bar.

I had a better idea. I told her to go somewhere that serves hot stuff in huge mugs. Hot chocolate, coffee, tea. Anything warm, nothing cold. And not just because it’s cold outside.

My advice draws on a popular study by Yale psychologist John Bargh (an advisee of Robert Zajonc), who studies nonconscious social behavior. Bargh asks: “What in our surroundings causes us to think, feel, and behave in ways without our intention or awareness?” The smell of lemon, for example, makes people feel compulsed to clean. The sound of Christmas music makes people want to shop longer.

And, it turns out, the feel of a warm cup in the hand makes people perceive others as warmer, i.e. more generous and caring. It’s a warm and fuzzy feedback loop, because people who hold warm cups act warmer, too. In Bargh’s experiment, people who held a warm cup were likely to be much more generous than people who were holding a cold cup. (One wonders: Are baristas warmer than sommeliers?)

In a second study, the researchers had subjects briefly hold either a cup of hot coffee or cold coffee before evaluating a stranger’s personality traits based on some stories. Subjects who had held the hot coffee assessed the person as being “warmer” on the likability scale than subjects who had held the iced coffee (4.7 vs 4.3). And there’s nothing magical about coffee: in other experiments, subjects who merely held a hot therapeutic pack judged others as warmer, and in turn acted more generously, than people who held ice packs.

What’s going on, according to the researchers, is a sort of conflation of physical and emotional warmth. A high temperature triggers activity in the insular cortex, an “old” brain structure that plays a role in processing both emotional and sensory experiences. It’s also the part of the brain that contains mirror neurons, which help people connect emotionally with others.

Of course, it all makes you wonder if the same phenomenon applies to climates. Is there any truth to the stereotype that Southerners are warm-hearted whereas Northerners are cold, Finns are temperamentally frigid and Haitians are hot? Is it any accident that the ice between couples melts when they go on beach vacations?

As instructed, my friend made her date wrap his hands around a mug of cocoa. It went well. He even called her later this evening to say how much he liked her. Of course, the feel-good dopamine blast from all the milk fat and sugar in the cocoa probably didn’t hurt either.