Scientists who study relationships have long focused on how couples handle love’s headaches, the cold silences and searing blowups, the childcare crises and work stress, the fallouts over money and ex-lovers.

But the way that partners respond to each other’s triumphs may be even more important for the health of a relationship, suggests a paper appearing in the current issue of The Journal of Personality and Social Psychology. The study found that the way a person responds to a partner’s good fortune — with excitement or passive approval, shared pride or indifference — is the most crucial factor in tightening a couple’s bond, or undermining it.

“When something good happens to your partner, it’s a terrific opportunity to strengthen the relationship — that’s what this study really says,” said Art Aron, a social psychologist at Stony Brook University in New York, who was not part of the study. “It fits with this whole thrust in the field, focusing on how to make things better rather than trying to avoid making them worse.”

In the study, researchers asked 79 heterosexual couples who had dated at least six months to fill out questionnaires characterizing how their partners typically reacted to positive news. People often had different styles in different contexts: a boyfriend who withdrew when his partner was upset or overwhelmed might glow with shared excitement if she was promoted. The researchers filmed the couples interacting in the lab, as they discussed positive events that happened to one or the other, to check their self-reports. The researchers also had members of the pairs rate how satisfied they were in the relationship, based on a battery of questions at the start of the study and again two months later.