Kissing:

"Since it is believed that various human courtship behaviors (like physical touching) may act to strengthen pair-bond attachments, it is not surprising to find that females also place greater value than males on these types of relationship activities (Denney, Field, & Quadagno, 1984; Hughes, Harrison, & Gallup, 2007; Hughes & Kruger, 2011; Johnson & Edwards, 1991; Symons, 1979). Romantic kissing may actually be one of the most effective bond-mediating courtship behaviors, with both males and females rating it as the type of physical affection ‘‘most expressive of love’’ (Gulledge et al., 2003). Recent neurological evidence suggests that romantic physical contact may function to mediate romantic pair-bonds by elevating levels of arousal, by activating the brain’s reward and motivational systems, or by initiating the release of neurotransmitters, opioids, and other neurohormones (Carter, 1998; Dunbar, 2010; Esch & Stefano, 2005; Fisher, Aron, & Brown, 2006; Light et al., 2005; Macdonald & Macdonald, 2010; Marazziti & Canale, 2004). Preliminary studies into romantic kissing confirm that it is women who seem to place greater overall importance on romantic kissing than men (Hughes et al.,2007), and that women in the late follicular phase of their cycle (at highest risk of conception) value kissing at initial relationship stages more than women in the luteal phase of their cycle (Wlodarski & Dunbar, 2013). Similarly, research also demonstrates that men are more likely to initiate kissing before sex, when it might be used for arousal purposes, whereas women are more likely to initiate kissing after sex, where it might better serve a relationship maintenance function (Hughes &Kruger, 2011). Women are also more likely to utilize kissing to assess a partner’s level of commitment throughout the relationship (Hughes et al., 2007). The evidence thus suggests that the ritual of romantic kissing serves several possible functions in the process of human mating: to assess the suitability of potential mates; to increase levels of autonomic arousal (and initiate coitus); and to mediate feelings of attachment in pair-bonded relationships."

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