Chapter
Four
Neuroscience
will come back to these later in this chapter. For now, we suggest that you keep
this basic experimental method in mind as we consider some complex ques-
tions raised by this research.
Some neuroscientists, especially Francis Crick and Christof Koch (2003), have
argued for ignoring the theoretical and philosophical problems and getting on
with the search for correlations across a wide range of conscious experiences.
I argue for a research program whose supreme aim is to discover the
neuronal correlates of consciousness, the NCC. These are the smallest set
of brain mechanisms and events sufficient for some specific conscious
feeling, as elemental as the color red or as complex as the sensual,
mysterious, and primeval sensation evoked when looking at the jungle
scene on the book jacket.
(Koch, 2004, pp. xv–xvi)When thinking about NCCs it is important to remember the usual warnings about
the meaning of ‘correlation’, above all that a correlation does not imply a cause.
This familiar trap is especially easy to fall into when dealing with something as
slippery as consciousness. When any correlation is observed between two events,
A and B, there are three possible causal explanations: A caused B; B caused A; or
some other event or process, C, caused them both. Alternatively, A and B might
actually be the same thing even though they do not appear to be.
In some cases, the right explanation is obvious. Imagine that you are at a rail-
way station and every so often you see hundreds of people gathering on the
platform, always followed by a train arriving. If correlation necessarily implied
cause you would have to conclude that the people on the platform caused
the train to appear. Obviously you won’t, because you know that both events
were caused by something else: a railway timetable. When it comes to con-
sciousness, however, things are not that obvious, and we can easily jump to
false conclusions. According to Dan Wegner’s (e.g. 2005) theory of conscious
will (Chapter 9), it is precisely this kind of confusion between correlation and
cause which creates the illusion that our thoughts cause our actions, when
in fact both are caused by prior neural activity. Similarly, we saw in Chapter 3
that rather than pictures in the head creating a rich and unified visual experi-
ence, it may be that the illusions of picture-like experiences and picture-like
mechanisms are both caused by the adaptive fitness of our visual and motor
systems.
So, when correlations are found between neural events and conscious experiences,
we must consider all these possibilities. Perhaps neural events cause conscious
experiences. Perhaps conscious experiences cause neural events. Perhaps some-
thing else causes both of them. Perhaps neural events are conscious experiences.
Perhaps we have so misconstrued one or the other that none of these is true.
CONSCIOUS VISION
Francis Crick, famous as the co-discoverer of the structure of DNA, was among the
first to look for the NCCs. Dismissing philosophy and adopting a thorough- going
reductionist approach, he argued that ‘that we shouldn’t approach the hard
Correlation is not
causation