Controlled experiments that have attempted to replicate Backster's findings have failed, and the theory was not accepted since it did not follow the scientific method. At the 141st annual meeting of American Association for the Advancement of Science, the panel of biologists found the claim unsupportable. The results seemed to be spontaneous; repeatability is still a problem, for him and the people who tried to perform his experiment. His lack of control experiments were criticized and explanations, such as that the polygraphs were responding to static electricity build-up and humidity changes, were put forward. The reliability of the polygraph test itself has been questioned. Plants have cellulose cell walls but do not possess sensory organs, which rules out the possibility of plants having ESP.