Experimental session and the social stress test
During the experimental session, participants' psycho-physiological responses to a variety of challenging conditions were recorded. These conditions included a spatial orienting task, a gambling task, a startle reflex task, and a social stress test. The session took place on weekends, in soundproof rooms with blinded windows. The total session started between 08:00 and 09:30 or between 12:00 and 14:30 and lasted about 3 h and 15 min. Although free salivary cortisol levels may be higher in the morning due to the circadian rhythm of cortisol production, morning and afternoon cortisol responses to social stress have been reported to be comparable (Kudielka et al., 2004). Participants were asked to refrain from smoking and from having coffee, milk, chocolate, and other sugar-containing foods 2 h before the test. The protocol was approved by the Central Committee on Research Involving Human Subjects. All participants gave informed consent.