Does wavefunction reduction require conscious observers?

Does the human body deviate from the laws of physics, as
gleaned from the study of inanimate nature? The traditional answer
to this question is ‘No’: the body influences the mind but the mind
does not influence the body. Yet at least two reasons can be given
to support the opposite thesis.?
Here we shall examine more closely the possibility that external
reality consists of a wavefunction and that this wavefunction only
reduces when an observation is made by a conscious observer. It is
the existence of consciousness that introduces the probabilistic
aspects into the quantum world.
One reason for at least considering such a suggestion is that
wavefunction reduction (which is an inexplicable phenomenon
associated with quantum theory) and decision making (which is an
inexplicable phenomenon associated with the conscious mind)
share the common feature of producing an increase of information;
in both something previously ‘unknown’ becomes ‘known’. More
specific motivation arise, as we have seen, from the following facts.
‘Simple’ systems apparently do not reduce wavefunctions; they are
also not conscious (we ignore here the possibility (c) of the previous
section). At some stage of ‘complexity’, and for reasons that may
be solely due to complexity or may involve something totally new,
there are systems that do reduce wavefunctions, and there are
systems that are conscious. In both cases our certainty here is due
to our own experience. We experience effects which appear to
correspond to reduced wavefunctions and we are certainly
conscious. It is therefore reasonable that we should try to relate the
two phenomena, an idea that has been argued most convincingly,
in recent times, by the eminent theoretical physicist, Eugene
Wigner. (It should be noted, however, that Wigner’s latest work on
this topic shows a move to the more conventional position that
other complex, yet not conscious, systems can also cause wavefunction
reduction. We refer, for example, to his article in
Quantum Optics, Experimental Gravity, and Measurement Theory
ed P Meystre and MO Scully [New York: Plenum 19831 .)
We must now explain carefully what is involved here. We
consider an isolated system, which may be as complicated as we
desire, but which must not contain any conscious mind. According
to our assumption, such a system is described by a wavefunction
which changes with time according to the rules of quantum theory.
A conscious observer now makes a measurement of some property
of this system, e.g. of the position of a particle. When the result
of this measurement enters the mind of the observer, then the
wavefunction reduces to the form corresponding to the particular
value of the measured quantity. Notice that it is not enough for the
conscious observer simply to be aware of only the part of the
wavefunction corresponding to the observed value. If this was all
that happened then we could not be sure that a different observer
would see the same value of the observed quantity. We require that
the act of conscious observation actually changes the wavefunction.
Thus, in our potential barrier experiment (see figures 15
and 16), if an observer sees the right-hand detector as being ON
then it must be ON, and not in the state of part ON and part OFF.
Then another observer will also see that it is ON, and both will
agree that the particle has been reflected. In figure 18 we illustrate
this difference between the observed and unobserved systems.
The last paragraph shows the first of the reasons noted by
Wigner, in the quotation at the start of this section, for believing
that mind affects physical things. The second reason he gives is that
in all other parts of physics, action and reaction occur together, i.e.
if A affects B then B affects A. Thus, since the physical world
clearly affects the conscious mind, we expect the converse to apply. To be quite fair, the assertion we have made here, that conscious
minds change the wavefunction, is not absolutely necessary. It
would, presumably, be possible that the act of observation does not
change the system, but that conscious observers somehow communicate
with each other so that they all ‘see’ the same thing. Such
an interpretation of quantum theory is possible and we shall discuss
it further in 54.5. We return to our assumption that only conscious observers can
reduce wavefunctions, and must now comment on how utterly
outrageous such a statement really is. To see this we might suppose
that the detectors in the potential barrier experiment are
photographic plates. What we are saying is that they are in a state
of ‘perhaps blackened but perhaps not’ until they have been
observed by a conscious mind, which may, of course, be years after
the event. Indeed, nothing ever really happens, e.g. no particle ever
decays, except through the intervention of a conscious mind. We
are not quite in the situation of denying external reality-which
possibility we considered and rejected in 0 1.2-but we are denying
that the external world possesses the properties we observe, until we
actually observe them. This is a picture of reality that we find hard
to accept.
The paradox of ‘Schrodinger’s cat’ is an example of the sort of
problem we can get into here. We suppose, for example, that the
right-hand detector in our potential barrier experiment is a trigger
that fires a gun and kills a cat as soon as a particle reaches it. After
one particle has passed through the apparatus the wavefunction
thus contains a piece in which the cat is dead and a piece in which
the cat is alive. Only if the cat is conscious can we say that one of
these represents the truth. What however could we say if the cat
were asleep? If, on the other hand, a cat is not conscious, or if we
used instead a being or a thing that is not conscious, then it remains
in a state of being part-dead/part-alive until some conscious
observer forces the wavefunction to go to one state or the other.
Like Schrodinger himself we probably consider this an unlikely
picture of reality.
The assumption we are considering appears even more weird
when we realise that throughout much of the universe, and indeed
throughout all of it at early times, there were presumably no conscious
observers. Thus the wavefunction did not reduce, and all the
possibilities inherent in the development of the wavefunction since
the beginning of time would have persisted until the first conscious
observers appeared. Even worse are the problems we meet if we
accept the modern ideas on the early universe in which quantum
decays (of the ‘vacuum’, but this need not trouble us here) were
necessary in order to obtain the conditions in which conscious
observers could exist. Who, or what, did the observations necessary
to create the observers? The only possibility here seems to be that observation, indeed
conscious observation, can be made by ‘minds’ outside the physical
universe. Such is one of the traditional roles of God and/or gods.
This is the realm of theology; a realm into which we shall, with
trepidation, enter briefly in the next section.
Before we close this section, however, there is one obvious
question we must ask. Since we have suggested that consciousness
might offer a possible, even if unlikely, solution to a problem of
physics, can physics help with the problem of the nature of consciousness?
Again the answer may well be that it cannot, but the
issue is certainly being discussed. The fact that quantum theory
frees physics from the rigid causality of classical mechanics is an
obviously immediately relevant fact. There just seems to be more
room for ideas like free will in a quantum world than in a classical
one. Already quantum tunnelling, as described in 81.3, has been
used to explain certain processes in the nervous system-see, for
example, Walker, International Journal of Quantum Chemistry 11
103 (1977). (We should, however, be cautious here. There is a big
difference between the idea of freedom to choose, where the choice
is presumably made by rational thought, and the apparent
randomness of quantum theory, so a relation between the two,
though possible, is not obvious,) It is also natural to try to associate
the very non-local nature of wavefunctions with the similar lack of
locality of ‘thoughts’, etc. For some discussion along these lines,
and for other references, we refer to the article by Stapp,
‘Consciousness and Values in the Quantum Universe’, Foundations
of Physics 15 35 (1985).