"We found that MDMA (1.5 mg/kg only) altered a behavioral indicator of social cognition. Specifically, it robustly reduced recognition of fearful faces, without changing recognition of other emotions from facial or vocal cues. Although previous studies have confirmed that the drug induces subjective feelings related to sociability and empathy, this is the first published demonstration of an overt behavioral effect of MDMA in humans."

Source

Bedi, Gillinder; Hyman, David; and de Wit, Harriet, "Is Ecstasy an “Empathogen”? Effects of 3,4-Methylenedioxymethamphetamine on Prosocial Feelings and Identification of Emotional States in Others," Biological Psychiatry (Dallax, TX: Society of Biological Psychiatry, December 15, 2010) Vol. 68, Issue 12, p. 1137.
http://www.ncbi.nlm.nih.gov/p…
http://www.ncbi.nlm.nih.gov/p…