Just in the past couple of days I have come across two different posts (1,2) about the hormone Oxytocin, and its use in a nosespray. These new studies are all really good examples of why we shouldn't pin down hormones or genes to a single function. For example, estrogens had been thought of for years as the "female hormones" and yet, it is estrogens that are necessary for male sexual behavior. In the case of oxytocin, it had long been called "the love hormone" because it, along with the closely related peptide vasopressin, has been shown to be involved in pair bonding (which is the scientist's rough equivalent of "falling in love and getting married"). Also, oxytocin is involved in childbirth and "labour" (which is why doctors give injections of it, or the analogue pitocin, to induce labour), and accordingly with its "love" moniker, it is believed that this surge of oxytocin helps the mother to bond to her offspring. Now, however, oxytocin is being linked to feelings of empathy, and trust, and it may even help autistic children who have difficulty with these emotions, leading them to interact more with their peers.
For more of a well-rounded, if off the wall, background on the subject of oxytocin, check out this site:
which reports on oxytocin as if it were a scandal in a tabloid.