In couple previous note strings, some requests have come up for information on psychological studies of meditation and enlightenment. There have been many psychological studies on meditation over the years, mostly on TM and, recently, on vipassana.
A study that I've found most helpful was done by Jack Engler and Daniel Brown, and is reported in the book "Transformations of Consciousness" by Ken Wilber, Jack Engler, and Daniel Brown (from Shambala Publications). I would highly recommend that anybody interested in psychology and meditation buy the book, because there is much more in it than the Brown/Engler study.
For those who don't have access, here's a brief summary.
Engler and Brown studied meditators who had gone through the 3 month retreat that the Insight Meditation Society runs every fall at their center in Barre, Mass. The study divided the retreat participants into three groups, with the teachers, who were not part of the retreat, as controls:
1) A group who had not exhibited any particular deepening of samadhi or vipassana during the retreat. They were primarily busy resolving psychological problems of varying depths that arose during the intense inner examination of the retreat.
2) A group who exhibited a deepening of samadhi, as a result of practicing the Therevadian jhanic meditation, as judged by their teachers.
3) A group who exhibited a deepening of insight, as a result of practicing vipassana meditation, as judged by their teachers.
Engler and Brown administered the Rorschach test to the participants before and after the retreat (I'm not a psychologist so I can't vouch for the effectivness of the Rorschach in testing for particular psychological characteristics, but it seems well accepted by certain psychotheraputic schools). The Rorschach's of the participants very clearly delineated the above three groups along the following lines:
1) Group 1 exhibited no change in their Rorschach results between the start and conclusion of the retreat.
2) The Rorschach tests from Group 2 had as their most outstanding characteristics "unproductivity" and a "paucity of associative elaborations." (Wilber, Engler, and Brown, pg. 177). The Rorschach test requires the subject to describe what an inkblot looks like, and meditators who exhibited deepened samadhi complained that it "took too much energy" to produce any images or associations of the inkblot. The most unusual finding reported by Engler and Brown was the high incidence of comments on the pure perceptual features of the inkblot. To subjects in the samadhi group, the inkblot looked exactly like an inkplot, and they tended to comment on pure determinants: form, pure color, shading, and inanimate movement.
3) The Rorschaches from Group 3 pointed in almost exactly the opposite direction of the samadhi group. They were primarily characterized by "increased productivity" and "richness of associative elaborations." As with the second group, the post retreat responses of this group exhibited very little overlap with their pre-retreat responses. The subjects tended to view the test as an opportunity to open to the flow of inner associations. Subjects employed one of two styles of elaboration, emphathetic or creative. The emphathetic style occurs when the subject puts him/herself into the precept. The creative style occurs when the subject changes his/her perspective on the precept many times during the test. The subjects seemed to be able to manifest a high degree of congruency between the flow of their internal world and the reality of the inkblot perception and test, something Engler and Brown characterize as "enhanced reality attunement." Finally, some subjects exhibited life affirming insights as part of their inkblot descriptions.
Engler and Brown ran another study on what they called "advanced insight practictioners." These are vipassana teachers who, by concensus of their teachers, had undergone the first Therevadan enlightenment experience, known technically as "stream entry". Most of these subjects were housewives in South Asia, a few were South Asian men, and several were Westerners, and their tests were corrected for cultural effects. Their Rorschachs did not exhibit the same outstanding qualitative features as those of the samadhi and insight groups, however, there were certain qualitative features that Engler and Brown characterized as "residual effects." The most unusual feature was the degree to which they perceived the inkblots as an interaction of form and energy or form and space. Several responses indicated types of energy organization associated with the human body, as conceptualized by one of the traditional Eastern systems of energy yoga.
Engler and Brown also report on a test of a single master, a man considered to have gone through the third Therevadian enlightnment stage, that of nonreturner. The first unusual characteristic of this subject's test was a shift in perspective. Whereas other subjects had considered the physical reality of the inkplot, this subject's responses indicated that he saw the inkblot as a projection of his mind, rather than that he was projecting his mind states onto the inkblot. The second unusual characteristic was that the subject was able to weave the entire test into a story based on the Buddhist philosophy of suffering and it's elimination. That is, the entire test was seen as an opportunity to teach Dharma. Engler and Brown comment that such a feat is quite remarkable, and that the only other example of such a Rorschach of which they were aware is a test on an Apache shaman, who used the test as an opportunity to teach about the Apache view of nature.
Again, I'd recommend that anyone who is interested in psychology and meditation buy the book. Also, I'd appreciate any information on more psychophysical studies, for example, using MRI or PET to study what parts of the brain get activated (or not) during meditation. Recently, PET studies have been used to study psychopathology and it would be interesting to see what PET studies on meditators would show.