In a trio of studies involving 130 people in long-term relationships, Maner and his colleagues found that to protect their own commitment to their partner, people would lash out at potential threats. In the first study, researchers asked students at Florida State University in long-term relationships to write about either a time when they felt intense love for their partner or a time when they felt intense sexual desire for the person — both positive relationship-related experiences. Next, the students looked at pictures of either an attractive or an unattractive man or woman, followed by a picture of a Chinese character. They were then asked to rate the appeal of the character; since the Chinese character is neutral, this question was meant to gauge the participants' leftover feelings about the real target of the study — the pictures of the men and women.

The students also filled out questionnaires about their basic levels of jealousy, answering questions such as, "How likely are you to surprise-visit your partner to see who is with him/her?"

The results showed that jealous sorts and more laid-back types rated the characters as about equally attractive when they'd thought of intense sexual desire for their partner. But when they thought about intense love for their partner, the jealous sorts suddenly became very negative about other attractive people, rating them much less appealing.

In a second study, the researchers upped the ante. They again had people in long-term relationships reflect on their love or sexual desire for their romantic partner, or some other nonrelationship-related story. But this time, the participants were told they were going to play a computer game with a partner in another room. Whoever lost got blasted with painful, but ultimately not harmful, bursts of white noise through headphones. The winner got to pick how long and how loud those blasts would be.

The researchers then showed the participants pictures of their alleged partners, who were always attractive and the same sex as the person in the experiment. Again, high-jealousy types who were reminded of their love for their partners treated this outside person harshly, blasting their eardrums with louder and longer stints of white noise.