There's a very interesting interview with Backster in The Sun Magazine:
I thought that if I put the galvanic-skin-response detector of the polygraph at the end of the leaf, a drop in resistance would be recorded on the paper as the moisture arrived between the electrodes. [...] I noticed something on the chart that resembled a human response on a polygraph: not at all what I would have expected from water entering a leaf. Lie detectors work on the principle that when people perceive a threat to their well-being, they respond physiologically in predictable ways. [...] at thirteen minutes, fifty-five seconds chart time, the thought entered my mind to burn the leaf. I didn't verbalize the idea; I didn't touch the plant; I didn't touch the equipment. Yet the plant went wild. The pen jumped right off the top of the chart. The only thing it could have been reacting to was the mental change.
If true, the implications are staggering. Yet, I've not been able to find conclusive rebuttal of his experiments. Considering the implication, you'd expect this question to be resolved conclusively one way or the other by now.
Can anyone provide links to results of independent experiments? Thanks.