"... about a fifth of a second."

From Deb Cunefare:

http://www.sciencedaily.com/releases/2010/10/101022184957.htm

"A new meta-analysis study conducted by Syracuse University Professor Stephanie Ortigue reveals falling in love can elicit not only the same euphoric feeling as using cocaine, but also affects intellectual areas of the brain. Researchers also found falling in love only takes about a fifth of a second."

Interesting article, I thought you'd like to see it. :)