Effects of Intranasal Oxytocin and Induced Stress on People's Belief Updating

In a randomized, double-blind, placebo controlled between-subjects design, healthy male volunteers receive intranasal oxytocin or placebo under stress or non-stress group prior belief updating task.

The Trier Social Stress Test (TSST) was used to induce psychosocial stress - this standardized technique enables a naturalistic exposure to a psychosocially stressful situation. This method consists primarily of a public speaking in second language (English) and a mental arithmetic task performed in front of a panel. Participants were not informed of the tasks prior to their recruitment. At the start of the TSST, they were told to prepare a 5-min speech to an unknown panel on personal suitability for their ideal job; the job description was matched to each participant, taking into consideration his personal aspirations. After the instructions, subjects were given 10 minutes of solitary preparation for this task. Then, they entered the TSST room and were told to start the presentation in front of a panel of two formally-dressed judges (one male and one female) and a conspicuous video camera. Any pause during the speech prompted a reminder from the judges of the remaining time. The interview was followed by 5 minutes of mental arithmetic performed out loud. Subjects were instructed to serially subtract 13 from 1022 as quickly and accurately as possible in front of the panel. If a mistake was made, the subject was told to start over from the beginning. After the mental arithmetic task, the TSST was concluded - subjects were confronted with the psychosocially stressful situation for a total of 10 minutes.

Non-stress groups first underwent a 5-minute session of travel magazine reading with two casually-dressed people (one male and one female), then did as many easy arithmetic questions within 5 minutes on paper. Participants were told that none of their answers would be marked.

All participants completed two sessions of self life event estimations, each with the same set of 40 adverse life events. The subjects were first presented with the events, then were instructed to estimate their likelihood (0-99%) of experiencing each event in the future (first Estimate, E1) and rate their confidence in their estimate. They were then presented with the actual probability of each event occurring to an average person in a similar environment (Feedback, F) and asked to rate their acceptance of the presented feedback. Five minutes after the first session, participants were instructed to perform the same task and provide their second estimate (E2) for the same 40 events in a randomized order and were, again, instructed to rate their confidence in their estimate. This time, however, no feedback was given. This process was repeated for a friend life event estimation session. After the second session, participants were given a surprise memory test for the presented feedback.