The purpose of this double blind, randomized, controlled, proof-of-concept study is to test the effects of cannabinoid receptor augmentation on the facilitation of fear conditioning. On three days over not more than two weeks, subjects will be trained to associate cues with two different stimuli, then this association will be extinguished. Cannabinoid receptor stimulation will be accomplished indirectly by harnessing the brain's capacity to endocannabinoids through the administration of an enzyme (FAAH inhibitor) that prevents degradation of anandamide. Subjects will receive placebo or the FAAH-inhibitor PF-04457845. Some details of this study have not been disclosed to preserve the study design.

Inclusion Criteria:

• Between the ages of 18 and 65
• Male and female
• No major medical problems

Exclusion Criteria:

• Hearing problems
• Psychiatric or mental problems