Perhaps when Axl Rose of Guns N’ Roses wrote “Don’t Cry,” he was really protecting his libido. First, researchers collected tears of women who watched sad movies. Later, males who smelled the tears had decreased testosterone and found pictures of females less appealing. fMRI scans of males’ brain activity after smelling tears revealed that males’ brains had less activity in regions associated with sexual arousal, which suggests that odorless tears contain a chemical signal that men unconsciously detect.
Gelstein, S., Yeshurun, Y., Rozenkrantz, L., Shushan, S., Frumin, I., Roth, Y., & Sobel, N. (2011). Humans tears contain a chemosignal. Science, 331 (6014), 226-230. doi: 10.1126/science.1198331