A friend once told me how, as a child visiting a zoo, his eyes focused  on one of the many monkeys in an enclosed exhibit. The monkey, in turn, began looking back. They remained locked in this visual embrace, until my friend turned away—to be startled when the monkey came flying at him right into the protective plexiglas. Only then did he notice the sign warning against staring at the monkeys, which take it as a sign of a challenge.

Staring into the eyes of any primate, humans included, is a great way to incite hostility. But done right, it can also increase feelings of closeness and affection and strengthen the bond between two people. This "soul gazing" and other exercises to keep love alive went on display last month in New York City and in San Francisco, with the help of Scientific American editor in chief Mariette DiChristina and Robert Epstein, a longtime psychology researcher who is also a contributing editor to Scientific American Mind. It was an audience participation version of Epstein's article, "Fall in Love and Stay That Way," in the January/February 2010 issue of Mind. Epstein has also posted a blog about this event, and you can hear selected parts of it with the Science Talk podcast version.

Another exercise, not in the video clip, is what Epstein calls the "I Love You" game. Here, a couple takes turn repeating those three little words in different ways: I LOVE you, I love YOU, I loooove you, Je t'aime, and so on. Just as in the soul-gazing exercise, love-related attitudes improved.

Later, I asked Epstein how attitudes would change if less emotionally charged terms were used, such as "I like you." The positive feelings would increase, he says, but not as much. "This is not because the meaning of the statement is particularly important but rather because of the taboos associated with each statement," he explains. "Saying 'I love you' to someone is extremely difficult in our culture—akin to showing yourself naked to someone. That's why it produces such a huge effect in this exercise."

And what about emotionally negative phrases? "Yes, repeating something hostile such as 'I hate you'—in an emotionally appropriate way—could indeed produce hostile feelings," he points out.

If that monkey could talk, I'm sure it would have said, "I hate you." Many, many times.