Kissing, romantic speech, or arousal increases alpha wave activity in the neocortex of romantic couples.

“What they found was there is a shift in brain waves, brain states, things like alpha waves or just a particular frequency of brain waves in the neocortex, the outer shell of the brain just beneath the skull. And in people that are kissing or in people that are engaged in romantic speech, or I didn't actually hear what they said to one another, but what the couple seems exciting, romantic and arousing to them, they see more alpha wave activity compared to the control conditions.”