Dr. Naranjo, studying the effects of yage on volunteers at the University of Chile, found that a number of the experiences were astonishingly similar to those reported to Dr. Harner by the Indians of Ecuador and Peru. Is the similarity of visions due to the drug itself ? Not necessarily, declares Dr. Harner, and adds: "I think it might be a little simplistic to automatically assume that these things are due to the drug. We don't know what they're due to. It's just that we do get these correlations between the experiences of the Indians in the upper Amazon and those urban whites that Dr. Naranjo experimented with. Just what causes the similarities is an entirely open question. It would be a mistake just to ascribe it to a biochemical reaction without more research being done."