Using an electronic scanner, the researchers found that the monks were producing a very strong pattern of gamma waves, a synchronized oscillation of brain cells that is associated with concentration and emotional control. A group of 10 college students who were learning to meditate produced a much weaker gamma signal.

Taken together, the studies suggest that "human qualities like compassion and altruism may in some sense be regarded as skills which can be improved through mental training," said Dr. Davidson, who is director of the Laboratory for Affective Neuroscience at the University of Wisconsin.

Yet the neuroscientists who have signed the petition say that there are several problems with this research. First, they say, Dr. Davidson and some of his colleagues meditate themselves, and they have collaborated with the Dalai Lama for years. Dr. Davidson said he helped persuade the spiritual leader to accept the society's invitation to speak, and was with him when he received the request.

The critics also point out that there are flaws in the 2004 experiment that the researchers have acknowledged: The monks being studied were 12 to 45 years older than the students, and age could have accounted for some of the differences. The students, as beginners, may have been anxious or simply not skilled enough to find a meditative state in the time allotted, which would alter their brain wave patterns. And there was no way to know if the monks were adept at generating high gamma wave activity before they ever started meditating.

"This paper has not tested the idea whether meditation promotes compassion or any kind of positive emotion," Dr. Yi Rao, a neuroscientist at Northwestern University who helped draft the petition and was one of the sharpest critics, said in an e-mail message.

"Nonetheless, advocates of Buddhism and meditation have confused the public with the claim that this idea has received scientific proof," Dr. Rao said. "If one reads the published scientific literature, it is not difficult to see that this claim is far from being proven. It will not hurt if the public also realizes that some researchers are declared believers playing dual roles as advocates and researchers."

In a telephone interview, Dr. Davidson said that the critics' assertions were overblown, given that the field of study was in its infancy and the studies so far had been exploratory.