by The Physics arXiv Blog
January 15, 2014
A new way of thinking about
consciousness is sweeping through science like wildfire.
Now physicists are using it to formulate
the problem of consciousness in concrete mathematical terms for the
There's a quiet revolution underway in theoretical physics. For as
long as the discipline has existed, physicists have been reluctant
to discuss consciousness, considering it a
topic for quacks and charlatans.
Indeed, the mere mention of the 'c'
word could ruin careers...
That's finally beginning to change thanks to a fundamentally new way
of thinking about consciousness that is spreading like wildfire
through the theoretical physics community.
And while the problem of
consciousness is far from being solved, it is finally being
formulated mathematically as a set of problems that researchers can
understand, explore and discuss.
a theoretical physicist at the Massachusetts Institute of Technology
in Cambridge, sets out the fundamental problems that this new way of
He shows how these problems can be
formulated in terms of quantum mechanics and information theory. And
he explains how thinking about consciousness (Consciousness
as a State of Matter) in this way leads to precise
questions about the nature of reality that the scientific process of
experiment might help to tease apart.
Tegmark's approach is to think of consciousness as a state of
matter, like a solid, a liquid or a gas.
"I conjecture that consciousness can
be understood as yet another state of matter. Just as there are
many types of liquids, there are many types of consciousness,"
He goes on to show how the particular
properties of consciousness might arise from the physical laws that
govern our universe.
And he explains how these properties
allow physicists to reason about the conditions under which
consciousness arises and how we might exploit it to better
understand why the world around us appears as it does.
Interestingly, the new approach to consciousness has come from
outside the physics community, principally from neuroscientists such
as Giulio Tononi at the University of Wisconsin in Madison.
In 2008, Tononi proposed that a system demonstrating consciousness
must have two specific traits:
First, the system must be able
to store and process large amounts of information. In other
words consciousness is essentially a phenomenon of
Second, this information must be
integrated in a unified whole so that it is impossible to
divide into independent parts. That reflects the experience
that each instance of consciousness is a unified whole that
cannot be decomposed into separate components.
Both of these traits can be specified
mathematically allowing physicists like Tegmark to reason about them
for the first time.
He begins by outlining the basic
properties that a conscious system must have.
Given that it is a phenomenon of
information, a conscious system must be able to store in a
memory and retrieve it efficiently.
It must also be able to process
this data like a computer, but one that is much more
flexible and powerful than the silicon-based devices we are
Tegmark borrows the term computronium
to describe matter (Consciousness
as a State of Matter) that can do this and cites other
work showing that today's computers underperform the theoretical
limits of computing by some 38 orders of magnitude.
Clearly, there is so much room for improvement that allows for the
performance of conscious systems.
Next, Tegmark discusses perceptronium, defined as the
most general substance that feels subjectively self-aware. This
substance should not only be able to store and process information
but in a way that forms a unified, indivisible whole.
That also requires a certain amount of
independence in which the information dynamics is determined from
within rather than externally.
Finally, Tegmark uses this new way of thinking about consciousness
as a lens through which to study one of the fundamental problems of
quantum mechanics known as the quantum factorization problem.
This arises because quantum mechanics describes the entire universe
using three mathematical entities:
an object known as a Hamiltonian
that describes the total energy of the system
a density matrix that describes
the relationship between all the quantum states in the
which describes how these things change with time
The problem is that when the entire
universe is described in these terms, there are an infinite number
of mathematical solutions that include all possible
quantum mechanical outcomes and many other even more exotic
So the problem is why we perceive the universe as the
semi-classical, three dimensional world that is so familiar.
When we look at a glass of iced water,
we perceive the liquid and the solid ice cubes as independent things
even though they are intimately linked as part of the same system.
Tegmark does not have an answer...
But what's fascinating about his
approach is that it is formulated using the language
of quantum mechanics in a way that
allows detailed scientific reasoning. And as a result it throws up
all kinds of new problems that physicists will want to dissect in
Take for example, the idea that the information in a conscious
system must be unified. That means the system must contain
error-correcting codes that allow any subset of up to half the
information to be reconstructed from the rest.
Tegmark points out that any information stored in a special network
known as a
Hopfield neural net automatically
has this error-correcting facility.
However, he calculates that a
Hopfield net about the size of the human brain with 1011
neurons, can only store 37 bits of integrated information.
"This leaves us with an integration
paradox: why does the information content of our conscious
experience appear to be vastly larger than 37 bits?" asks
That's a question that many scientists
might end up pondering in detail.
For Tegmark, this paradox suggests that
his mathematical formulation of consciousness is missing a vital
"This strongly implies that the
integration principle must be supplemented by at least one
additional principle," he says.
And yet the power of this approach is in
the assumption that consciousness does not lie beyond our ken; that
there is no "secret sauce" without which it cannot be tamed.
At the beginning of the 20th century, a group of
young physicists embarked on a quest to explain a few strange but
seemingly small anomalies in our understanding of the universe.
In deriving the new theories of
relativity and quantum mechanics, they ended up changing
the way we comprehend the cosmos. These physicists, at least some of
them, are now household names.
Could it be that a similar revolution is currently underway at the
beginning of the 21st century...?