The notion that human consciousness can supervene the material principles of physics is often found in the literature on parapsychology and complementary medicine. In a recent paper in the British Medical Journal entitled "History and Mystery Ð Retroactive prayer: a preposterous hypothesis?" Brian Olshansky and best-selling author Larry Dossey claim that prayers offered 4-10 years later can shorten the length of hospital stays and fever duration of septic patients. They refer to a paper published earlier in the same journal by Leonard Leibovici.
A quick look at the data show that they lack the statistical significance to justify such a world-shaking conclusion. The p-value is merely 4 percent, a result to be expected as a random artifact in 1 of every 25 experiments or fewer. We can easily imagine 24 experiments with a lesser effect never being published. I have lamented before in this column about the inappropriateness of the 5 percent p-value threshold, common in medical journals, for the publication of extraordinary claims.
Olshansky and Dossey argue that quantum mechanics provides a physical basis for retroactive prayer. They refer to experiments by Helmut Schmidt in which humans attempt to mentally affect radioactive decays, which are inherently quantum events. While Schmidt claims positive results, his experiments also lack adequate statistical significance and have not been successfully replicated in the thirty-five years since his first experiments were reported.
The claim that quantum mechanics implies that human consciousness can control physical events can be traced to a wrongful interpretation of the famous wave-particle duality. Popular, non-technical literature will often report that quantum mechanics shows that an object is either a wave or a particle, depending on what you measure. If you measure its wavelength, then it is a wave. If you measure its position, then it is a particle. Since measurement is an act of human consciousness, then the implication is that thought processes in fact determine reality.
Human consciousness is also frequently invoked as the mechanism for the so-called "collapse" of the wave function when a measurement is made. We can find no basis for this in quantum theory, where some formulations do not contain wave function collapse, or even wave functions.
The popular picture of particles as somehow also being waves is a pedagogical simplification used to "explain" interference and diffraction effects in familiar terms. All experiments detect particles and our theories describe these particles as the "quanta" of quantum fields and not as "waves." This theoretical description does not imply a dual reality in which one form of reality is changed to another by the act of measurement or some human thought.
Olshansky and Dossey also suggest that modern quantum physics provides a plausible mechanism for the backward causality implied by retroactive prayer. While the results of some quantum experiments may be interpreted as evidence for events in the future affecting events in the past at the quantum level, no theoretical basis exists for applying this notion on the macroscopic scale of human experience.
The fundamental equations of physics do not distinguish past from future, or cause from effect. As shown by Boltzmann in the 1870s, the "arrow of time" of common experience is a statistical effect present in systems of many particles that are away from equilibrium. As the result of the random motions of its particles, such systems will more likely approach equilibrium than move away from it. That more likely direction is defined as the direction of time, and is codified in the second law of thermodynamics in which isolated systems tend toward maximum entropy. Since the systems we humans deal with in everyday life typically contain 1024 particles or more, the probability for highly randomized events occurring in one time direction is far greater than the other direction. Thus, our experience is that a broken glass does not reassemble, although this could in principle happen if the molecules are moving, by chance, in the right direction.
In short, while the fundamental atomic and subatomic processes of many body systems proceed in a time-symmetric fashion, our common experience is one of directed time. This includes the human body, and even those parts, such as cells, that are normally considered "microscopic" are too large and contain too many particles to exhibit quantum effects in their collective behavior. For example, the motions of the vesicles that carry signals across synapses and constitute part of the mechanism for our thinking processes can be described without recourse to quantum mechanics. Of course, the atoms in biological systems are quantum in nature, but their collective behavior does not seem to exhibit any quantum effects. While many-body quantum systems such as lasers and superconductors exist, no convincing evidence supports proposals that the brain is somehow a quantum device. What is more, even if the brain were a quantum system, that would not imply that it can break the laws of physics any more than electrons or photons, which are inarguably quantum in nature.
In a number of places, Olshansky and Dossey use the term "nonlocal," although to what purpose is never clear. Nonlocality refers to the apparent spacelike correlations exhibited between separated parts of some quantum systems. That is, these correlations exist over distance and time intervals that can only be connected by a signal moving faster than the speed of light. It is amusing that the problem of nonlocality disappears when we allow backward causality, exactly the phenomenon that Olshansky and Dossey wish to exploit. They can't have both. In any case, while nonlocality and backward causality remain controversial topics in discussions on the philosophical foundations of quantum mechanics, they have nothing to do with religion, medicine, or parapsychology.