 - At the second visit, participants will provide another saliva sample; receive oxytocin, arginine vasopressin, placebo, or no drug at all; and have tests of pain sensitivity and a pain-relieving procedure. During the pain-relieving procedure, participants will receive brief, moderately painful electrical shocks on the back of the nondominant hand and a low-level electrical stimulation on the middle finger that counteracts or reduces the pain from the shocks. Participants will rate their pain perception at the end of each stimulation by using a visual scale ranging from 0 no pain to 10 maximum imaginable pain. The experiment ends with a final saliva collection and completion of the psychological questionnaires... 