Dean Radin

The role of observation in quantum mechanics remains one of the most persistent open questions in science. From the earliest formulations of quantum theory, it was clear that measurement plays a special role, yet precisely what that role entails is still debated. One of the more provocative ideas, associated with proposals by von Neumann and others, is that conscious observation is required to collapse the quantum wavefunction. While this idea has long occupied a marginal position in physics, it continues to attract serious interest at the intersection of quantum theory, philosophy of mind, and consciousness studies. Of greater importance, the idea is testable. The title of this talk reflects both the unconventional status of the consciousness-collapse hypothesis and the fact that many of the relevant experiments have involved conscious modification of interference fringes in quantum optical systems. In this talk, I review experimental efforts that have explicitly or implicitly tested observer-dependent collapse. Although the experiments differ widely in methods and interpretations, and their results have evoked vigorous debate, they collectively form a body of empirical work reported by 10 laboratories. These results are not uniformly accepted, but they are also not easily dismissed, and they point toward an interpretation that mainstream physics has studiously avoided for decades.