To smile, or not to smile. Research shows that men are generally more attractive when they don't show their pearly whites. But that's not all bad news for those who can't keep smiling. A new study says that women consider those who smile as relationship material.

The study was conducted from the University of Oslo and Senshu University in Japan, gathering 218 women to rate European and East Asian subjects who were smiling or had a neutral expression on an attractiveness scale.

The study found that 71 women rate smiling and neutral-faced men on masculinity and trustworthiness.

Men who smiled seemed less masculine, but were more trustworthy and mature than neutral expressions.

But when they weren't smiling, they come off as more masculine, which women prefer for hookups instead.

Example: Relationship Thor:

Hookup Thor: