Fear of Spiders

This clinical trial aims to evaluate the nature and duration of effects of three FDA-approved medications (propranolol and hydrocortisone) on military-relevant cognitive, emotional, and motor performance following an exposure to a stressful situation (i.e., exposure to a tarantula) in physically healthy adult volunteers (aged 18 - 40) with fear of spiders to help the future development of medications for treating Acute Stress Reactions. The main questions this study aims to answer are: Will placebo treatment (oral placebo) result in significant decrements in Psychomotor Vigilance Task (PVT) performance compared to propranolol treatment? Will placebo treatment \[intramuscular (IM) placebo\] result in significant decrements in PVT performance compared to hydrocortisone treatment? Participants will receive one of five study medications (oral propranolol, oral placebo, IM hydrocortisone, or IM placebo) after a brief exposure to a tarantula. Participants will complete cognitive and simple motor tasks and psychological assessments before and after the study medication administration.