Researchers in the United States and Norway are working together to figure out what forms of flirtation are most effective and why.

The results of the international collaboration are only based on questionnaires, not experiments, which means we have to assume participants are being honest and self-aware about what they find attractive.

That said, among 415 men and women in Norway and 577 in the US, there was one way of flirting that stood out among heterosexual relationships.

Whether looking for a fling or a long-term romance, humor was generally deemed the most effective str...