A friend asked me to inquiry if there are any "hard" science studies on the effectiveness (or ineffectiveness) of Zen practice, including what "enlightenment experiences" (i.e., kensho, satori) entail. She is not interested in anything by actual practitioners of Zen or Buddhism (e.g., a psychologist who is also a Zen practitioner or the Dalai Lama's work at MIT). She is only interested in studies by independent "completely objective" scientists outside of the practice.

Any ideas?

Thanks!
Keith