Biobehavioral Correlates of Acute Phobic Fear

Inclusion Criteria: * 18 - 40 years old * Phobic or nonphobic fear of spiders. * Willing to proceed through 5-stimulus fear hierarchy or maintain 7 or higher subjective units of distress through fear task (see Procedures section). Exclusion Criteria: * Lifetime history of serious mental illness * Lifetime history of intellectual or developmental delays * Lifetime history of chronic physical or medical illness including blood clotting disorders * Lifetime history of allergies to latex * Lifetime history of hormonal replacement therapy * Lifetime history of blindness * Lifetime history of blood/injection phobia or aversion to needles/injection (based on IPS-Anx and MQ) * Substance abuse in the past 2 years * Cigarette/tobacco use in the past 2 years * Major depression within the past 12 months * Traumatic stress within the past 12 months * Pregnancy within the past 12 months * Anesthesia within the past 3 months * Night shift work within the past month * Use of medication within the past month (except for oral contraception) * Acute illness or infection within the past month * Average sleep outside of 6 - 10 hours per night within the past month * Average intake of 4 or more alcoholic beverages per week * Average intake of 6 or more cups caffeine per day * Use of marijuana within the week before the laboratory session * Use of alcohol within the week before the laboratory session * Body mass index outside of 18.5 - 24.9 range