RIO RANCHO, N.M. -- One night last month, Jean-Pierre Larroque drove into the desert here, lay down in the road and waited for one of his best friends to waterboard him.

Just a few hours earlier, the 26-year-old Peace Corps volunteer had been debating with two close friends whether waterboarding is torture. Finishing up a pizza dinner, Mr. Larroque casually suggested that the three settle the matter by trying it out for themselves.

They...