A little bit of masculine scent loaded with sexual pheromones is the recipe to make a female drop into a man's lap. Moreover, male pheromones not only change a female's brain's activity, but also its size! At least in mice, as recently discovered by scientists.

The growth of their brain apparently made females rodents choose more powerful mice. Many insects and mammals attract a mate by employing the chemical trick, the pheromones. But the brain nuclei targeted by the pheromones are also where most new neurons emerge in the adult brain: the olfactory bulb, which picks up the scents, and the hippocampus, which stocks memories.

In the new research, the scientists found that pheromones from dominant male mice stimulated the growth of new neurons in female brains; but when the females were exposed to scents of lower rank or castrated males, their brain anatomy remained unchanged.

Female mice usually choose alpha males, but when the scientists impaired the brain growth in the areas usually stimulated by male pheromones, the female mice lost their preference for mighty males. The team found that female pheromones, too, induced growth in male brains, but less significant, and they also detected the hormones connected with this brain growth.

"These kinds of hormones could potentially be useful when it comes to repair or improvement of function of a damaged brain in humans in situations of injury and disease," explained researcher Samuel Weiss, a neuroscientist at the University of Calgary.

"The question of whether or not pheromones influence human sexiness is of continuing interest to scientists, the public and the $10-billion-per year perfume industry," said neurobiologist Zhengui Xia at University of Washington in Seattle, not involved in this research.

"I don't believe there's any evidence suggesting that pheromones play as critical a role in reproduction in humans as they do in mice, but people do talk a lot about the intangibles they believe bring people together. Pheromones might in some regard play an important role in types of bonding we don't recognize yet," said Weiss.

Thus, in the end, this may be the way men make women lose their heads...