Quantum Theory and Consciousness
Another highly nerdy and technical blog entry…

I've been working on the last couple chapters of my long-due philosophy-of-mind book "The Hidden Pattern", and one of the chapters is on quantum reality, so I've been re-studying some of the trickier aspects of quantum theory and its interpretation.

In the course of this, I've come to what I think is a clearer understanding of the relation between quantum theory and consciousness, based on the "decoherence" approach to quantum measurement -- see


for a refresher on this topic.

This blog entry will make the most sense to readers who are at least a little familiar with quantum theory, at least at the popular-science level.

Unlike what Eugene Wigner suggested back in the 1960’s, we can’t quite say consciousness is the collapse of the wave function” because in the decoherence approach the wave function does not collapse – there are merely some systems that are almost-classical in the sense that there is minimal interference between the different parts of their wave function.

Of course, we can always say “everything is conscious” but this doesn’t really solve anything – even if everything is conscious, some things are more conscious than others and the problem of consciousness then is pushed into defining what it means for one thing to have a higher degree of consciousness than another.

The analogue of “consciousness is the collapse of the wave function” in the decoherence approach would seem to be “consciousness is the process of decoherence.” I propose that this is actually correct in a fairly strong sense, although not for an entirely obvious reason.

Firstly, I suggest that we view consciousness as “the process of observing.” Now, “observation,” of course, is a psychological and subjective concept, but it also has a physical correlate. I suggest the following characterization of the physical substrate of observation: Subjective acts of observation physically correspond to events involving the registration of something in a memory from which that thing can later be retrieved.

It immediately follows from this that observation necessarily requires an effectively-classical system that involves decoherence.

But what is not so obvious is that all decoherence involves an act of observation, in the above sense. This is because, as soon as a process decoheres, the record of this process becomes immanent in the perturbations of various particles all around it – so that, in principle, one could deconstruct the process from all this data, even though this may be totally impractical to do. Therefore every event of decoherence counts as an observation, since it counts as a registration of a memory that can (in principle) be retrieved.

Most events of decoherence correspond to registration in the memory of some fairly wide and not easily delineated subset of the universe. On the other hand, some events of decoherence are probabilistically concentrated in one small subset of the universe – for example, in the memory of some intelligent system. When a human brain observes a picture, the exact record of the picture cannot be reconstructed solely from the information in that brain – but a decent approximation can be. We may say that an event of registration is approximately localized in some system if the information required to reconstruct the event in an approximate way is contained in that system. In this sense we may say that many events of consciousness are approximately localized in particular systems (e.g. brains), though in an exact sense they are all spread more widely throughout the universe.

So, just as the Copenhagen-interpretation notion of “wave function collapse” turns out to be a crude approximation of reality, so does the notion of “wave function collapse as
consciousness.” But just as decoherence conceptually approximates wave function collapse, so the notion of “decoherence as registration of events in memory as consciousness” conceptually approximates “wave function collapse as consciousness.”

How is this insight reflected in the language of patterns (the theme of my philosophy book – “everything is pattern”)? If a system registers a memory of some event, then in many cases the memory within this system is a pattern in that event, because the system provides data that allows one to reconstruct that event. But the extent to which a pattern is present depends on a number of factors: how simple is the representation within the system, how difficult is the retrieval process, and how approximate is the retrieved entity as compared to the original entity. What we can say is that, according to this definition, the recognition of a pattern is always an act of consciousness. From a physics point of view, though, not all acts of consciousness need to correspond to recognitions of patterns. On the other hand, if one takes a philosophical perspective in which pattern is primary (the universe consists of patterns) then it makes sense to define pattern-recognition is identical to consciousness (???)

Of course, none of this forms a solution to the "hard problem of consciousness," which may be phrased as something like "how does the feeling of conscious experience connect with physical structures and dynamics?" This is philosophically subtler issue and you'll have to wait for "The Hidden Pattern" to read my views on it these days (which are different from anything I've published before). But an understanding of the physical correlates of consciousness is a worthwhile thing in itself, as well as a prerequisite to an intelligent discussion of the “hard problem.”

What do you think?