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.