Some
problems in science are so hard, we don’t really know what meaningful
questions to ask about them — or whether they are even truly solvable by
science. Consciousness is one of those: Some researchers think it is an
illusion; others say it pervades everything. Some hope to see it
reduced to the underlying biology of neurons firing; others say that it
is an irreducibly holistic phenomenon.
The question of what kinds of physical systems are conscious “is one of the deepest, most fascinating problems in all of science,” wrote the computer scientist Scott Aaronson
of the University of Texas at Austin. “I don’t know of
any philosophical reason why [it] should be inherently unsolvable” — but
“humans seem nowhere close to solving it.”
Now a new project currently under review hopes to close in on some
answers. It proposes to draw up a suite of experiments that will expose
theories of consciousness to a merciless spotlight, in the hope of
ruling out at least some of them.
If all is approved and goes according to plan, the experiments could
start this autumn. The initial aim is for the advocates of two leading
theories to agree on a protocol that would put predictions of their
ideas to the test. Similar scrutiny of other theories will then follow.
Whether or not this project, funded by the Templeton World Charity Foundation,
narrows the options for how consciousness arises, it hopes to establish
a new way to do science for difficult, contentious problems. Instead of
each camp championing its own view and demolishing others, researchers
will collaborate and agree to publish in advance how discriminating
experiments might be conducted — and then respect the outcomes.
Dawid Potgieter,
a senior program officer at the Templeton World Charity Foundation who
is coordinating the endeavor, says that this is just the beginning of a
sustained effort to winnow down theories of consciousness. He plans to
set up several more of these “structured adversarial collaborations”
over the next five years.
He is realistic about the prospects. “I don’t think we are going to
come to a single theory that tells us everything about consciousness,”
he said. “But if it were to take a hundred years to solve the mystery of
consciousness, I hope we can cut it down to fifty.”
A Workspace for Awareness
Philosophers have debated the nature of consciousness and whether it
can inhere in things other than humans for thousands of years, but in
the modern era, pressing practical and moral implications make the need
for answers more urgent. As artificial intelligence (AI) grows
increasingly sophisticated, it might become impossible to tell whether
one is dealing with a machine or a human merely by interacting with it —
the classic Turing test. But would that mean AI deserves moral
consideration?
Understanding consciousness also impinges on animal rights and
welfare, and on a wide range of medical and legal questions about mental
impairments. A group of more than 50 leading neuroscientists,
psychologists, cognitive scientists and others recently called for
greater recognition of the importance of research on this difficult
subject. “Theories of consciousness need to be tested rigorously and
revised repeatedly amid the long process of accumulation of empirical
evidence,” the authors said, adding that “myths and speculative
conjectures also need to be identified as such.”
You can hardly do experiments on consciousness without having first
defined it. But that’s already difficult because we use the word in
several ways. Humans are conscious beings, but we can lose
consciousness, for example under anesthesia. We can say we are conscious
of something — a strange noise coming out of our laptop, say. But in
general, the quality of consciousness refers to a capacity to experience
one’s existence rather than just recording it or responding to stimuli
like an automaton. Philosophers of mind often refer to this as the
principle that one can meaningfully speak about what it is to be “like” a
conscious being — even if we can never actually have that experience
beyond ourselves.
Plenty of cognition takes place outside the grasp of conscious
awareness — in that sense, we respond to some cues and stimuli
“unconsciously.” A distinguishing feature of our minds, however, is that
we can hold on to a piece of information, an idea or an intention as a
motivation for subsequent decisions and behaviors. If we’re hungry, we
salivate as a reflex, but we might also choose to eat, go to the kitchen
and get what we want from the cupboard.
Some researchers, such as the cognitive scientist Stanislas Dehaene of the Collège de France in Paris, suggest that this conscious behavior arises when we hold a piece of information in a “global workspace”
within the brain, where it can be broadcast to brain modules associated
with specific tasks. This workspace, he says, imposes a kind of
information bottleneck: Only when the first conscious notion slips away
can another take its place. According to Dehaene, brain-imaging studies
suggest this “conscious bottleneck” is a distributed network of neurons
in the brain’s prefrontal cortex.
This picture of consciousness is called global workspace theory
(GWT). In this view, consciousness is created by the workspace itself —
and so it should be a feature of any information-processing system
capable of broadcasting information to other processing centers. It
makes consciousness a kind of computation for motivating and guiding
actions. “Once you have information and the information is made broadly
available, in that act consciousness occurs,” said Christof Koch, chief scientist and president of the Allen Institute for Brain Science in Seattle.
Lucy Reading-Ikkanda/Quanta Magazine
But to Koch, the argument that all of cognition, including
consciousness, is merely a form of computation “embodies the dominant
myth of our age: that it’s just an algorithm, and so is just a clever
hack away.” According to this view, he said, “very soon we’ll have
clever machines that model most of the features that the human brain has
and thereby will be conscious.”
He has been developing a competing theory in collaboration with its originator, the neuroscientist Giulio Tononi
of the University of Wisconsin-Madison. They say that consciousness is
not something that arises while turning inputs into outputs but rather
an intrinsic property of the right kind of cognitive network, one that
has specific features in its architecture. Tononi christened this view integrated information theory (IIT).
In contrast to GWT, which starts by asking what the brain does to
create the conscious experience, IIT begins instead with the experience.
“To be conscious is to have an experience,” Tononi said. It doesn’t
have to be an experience about anything, although it can be; dreams, or
some “blank mind” states attained by meditation also count as conscious
experiences. Tononi has sought to identify the essential features of
these experiences: namely, that they are subjective (they exist only for
the conscious entity), structured (their contents relate to one
another: “the blue book is on the table”), specific (the book is blue,
not red), unified (there is only one experience at a time) and
definitive (there are bounds to what the experience contains). From
these axioms, Tononi and Koch claim to have deduced the properties that a
physical system must possess if it is to have some degree of
consciousness.
Lucy Reading-Ikkanda/Quanta Magazine
IIT does not portray consciousness as information processing but
rather as the causal power of a system to “make a difference” to itself.
Consciousness, Koch said, is “a system’s ability to be acted upon by
its own state in the past and to influence its own future. The more a
system has cause-and-effect power, the more conscious it is.”
This harks back to the famous “cogito, ergo sum” dictum of René
Descartes in the 17th century. “The one thing, the only thing, that is
[a] given is my experience,” Koch said. “That’s Descartes’ central
insight.”
To Tononi and Koch, systems in which information is merely “fed
forward” to convert inputs to outputs, as in digital computers, can only
be “zombies,” which might act as if they are conscious but cannot
truly possess that property. Much of Silicon Valley may believe that
computers will eventually become conscious, but to Koch, unless those
machines have the right hardware for consciousness, they will just
constitute a “deep fake.”
“Digital computers can simulate consciousness, but the simulation has
no causal power and is not actually conscious,” Koch said. It’s like
simulating gravity in a video game: You don’t actually produce gravity
that way.
‘Surrounded and Immersed’ in Consciousness
One of the most striking features of IIT is that it makes
consciousness a matter of degree. Any system with the required network
architecture may have some of it. “No matter whether the organism or
artifact hails from the ancient kingdom of Animalia or from its recent
silicon offspring, no matter whether the thing has legs to walk, wings
to fly, or wheels to roll with,” Koch wrote in his 2012 book Consciousness: Confessions of a Romantic Reductionist. “If it has both differentiated and integrated states of information, it feels like something to be such a system.”
This view arouses a lot of skepticism. The influential American philosopher of mind John Searle of the University of California, Berkeley derides the idea as a form of panpsychism: crudely, a belief that mind and awareness infuse the whole cosmos. In a withering critique of IIT,
Searle has asserted that “the problem with panpsychism is not that it
is false; it does not get up to the level of being false. It is strictly
speaking meaningless because no clear notion has been given to the
claim.” Consciousness, he wrote, “cannot be spread over the universe
like a thin veneer of jam” — it “comes in units and panpsychism cannot
specify the units.”
Koch, however, is perfectly happy to think that “we are surrounded
and immersed” in consciousness. He believes “that consciousness is a
fundamental, elementary property of living matter. It can’t be derived
from anything else.”
But this doesn’t mean it is spread equally everywhere. Koch and
Tononi assert that, while consciousness can be an attribute of many
things, a significant amount of it can exist only in particular kinds of
things, notably human brains (indeed, in specific parts of human
brains). And to turn IIT into a quantitative, testable theory, Koch and
Tononi have formulated a criterion for what kinds of things those are.
To reflect how conscious an information-processing network is, Koch
and Tononi define a measure of “information integration,” which they
call Φ (the Greek letter phi). It represents the amount of “irreducible
cause-effect structure”: how much the network as a whole can influence
itself. This depends on interconnectivity of feedback. If a network can
be divided into smaller networks that don’t exert causal power on one
another, then it will have a correspondingly low value of Φ no matter
how many processing nodes it has.
Equally, “any system whose functional connectivity and architecture
yield a Φ value greater than zero has at least a trifle of [conscious]
experience,” Koch said. That includes the biochemical regulatory
networks found in every living cell, and also electronic circuits that
have the right feedback architecture. Since atoms can influence other
atoms, “even simple matter has a modicum of Φ.” But systems that have
enough Φ to “know” of their existence, as we do, are rare (although the
theory anticipates that higher animals will also have a degree of that
experience).
Because of this effort to make IIT quantitative and testable, Aaronson puts it
“in something like the top 2 percent of all mathematical theories of
consciousness ever proposed.” He believes that the theory is flawed —
but contrary to Searle, he says that “almost all competing theories of
consciousness have been so vague, fluffy and malleable that they can
only aspire to wrongness.”
Seeking Neural Correlates
Koch would concur with that. “Everybody seems to have a pet theory of
consciousness, but few of them are quantitative or predictive,” he
said. He believes that both GWT and IIT are testable. “Logically
speaking, they could be wrong, or both could capture certain aspects of
reality.” How, though, do we test them?
Enter the Templeton World Charity Foundation, which has assigned $20
million to the task of testing theories of consciousness to destruction.
It is starting with what Potgieter calls a “structured adversarial
collaboration” involving IIT and GWT because they are able to make
testable and contrasting predictions. The plan is for the proponents of
the two theories to agree in advance to an experimental protocol that
ought to distinguish whether either or both of the theories are wrong.
“The condition was that the leaders of the theories would sign off on
this protocol, in the sense of acknowledging that the predictions
accurately represent the theory,” Potgieter said. (He credited the
willingness of Dehaene and Tononi “to put themselves on the line” as one
of the considerations that led to the choice of GWT and IIT as the
first theories on the block.)
The collaboration will get a top journal to commit to publishing the
outcome of the experiments, come what may. The study will also include
replication experiments. “This is basically open science,” Potgieter
said. “If we can use the best practices in open science to demonstrate
progress in an area where no one has done very much, it could show that
it’s a useful approach.”
He says that the researchers now have a final experimental design to
test incompatible predictions of GWT and IIT head-to-head. The details
are yet to be disclosed, but they will deploy a battery of
brain-monitoring techniques, such as functional magnetic resonance
imaging (fMRI), electrocorticography and magnetoencephalography. The
experiment seems to be “the first time ever that such an audacious,
adversarial collaboration has been undertaken and formalized within the
field of neuroscience,” Potgieter added. He hopes that if the project is
approved, the experimental work will be able to start after the summer
and run for about three years, involving 10-12 labs.
What differences between the theories will the experiments test? One
is in the location of consciousness in the brain. According to GWT, the
“neural correlates of consciousness” — the patterns of neuron activity
that reflect the conscious state — should show up in parts of the brain
that include the parietal and frontal lobes of the cortex. The parietal
lobe processes sensory data such as touch and spatial sense. The frontal
lobe is associated with cognitive processing for “higher” functions
such as memory, problem solving, decision-making and emotional
expression.
But people who have had a large fraction of the frontal lobe removed —
as used to happen in neurosurgical treatments of epilepsy — can seem
remarkably normal, Koch says. According to IIT, the seat of
consciousness is instead likely to be in the sensory representation in
the back of the brain, where the neural wiring seems to have the right
character. “I’m willing to bet that, by and large, the back is wired in
the right way to have high Φ, and much of the front is not,” Tononi
said.
We can compare the locations of brain activity in people who are
conscious or have been rendered unconscious by anesthesia, he says. If
such tests were able to show that the back of the brain indeed had high Φ
but was not associated with consciousness, he admits that “IIT would be
very much in trouble.”
A recent fMRI study
of brain activity in volunteers who were either conscious or under
general anesthesia, conducted by a group that included Dehaene, showed
distinct patterns corresponding to the two states. During periods of
unconsciousness, brain activity persisted only among regions with direct
anatomical connections, whereas during conscious activity, complex
long-distance interactions did not seem constrained by the brain’s
“wiring.”
However, one of the authors of the study, the physicist-turned-neuroscientist Enzo Tagliazucchi
of the University of Buenos Aires and the Pitié-Salpêtrière Hospital in
Paris, stresses that the findings don’t yet clearly support any
particular theory of consciousness. “It would be premature to frame our
work within one theory or the other,” he said. “It doesn’t tip any
balance, nor it is intended to do so.”
Another prediction of GWT is that a characteristic electrical signal
in the brain, arising about 300-400 milliseconds after a stimulus,
should correspond to the “broadcasting” of the information that makes us
consciously aware of it. Thereafter the signal quickly subsides. In
IIT, the neural correlate of a conscious experience is instead predicted
to persist continuously while the experience does. Tests of this
distinction, Koch says, could involve volunteers looking at some
stimulus like a scene on a screen for several seconds and seeing whether
the neural correlate of the experience persists as long as it remains
in the consciousness.
Not everyone is optimistic that it will be possible to find rigorous,
definitive ways of testing and adjudicating these two theories. “The
current project is an attempt in good faith in this direction,” said Francis Fallon,
a philosopher of mind at St. John’s University in Queens, New York, who
is involved in the Templeton project. But he noted that because both
theories have already been shaped by existing empirical evidence, it
would be surprising to find new data with which either seems
fundamentally inconsistent.
Hakwan Lau,
a psychologist who studies behavioral neuroscience at the University of
California at Los Angeles, is not convinced IIT is even a truly
scientific theory. “IIT is based on armchair theorizing,” he said. He
thinks that what IIT advocates regard as the likely locus of
consciousness doesn’t necessarily follow from the theory but is just
their subjective view. “To make empirical predictions [of the theory]
testable by current methods,” he said, “many additional assumptions and
approximations need to be made.”
To him, Lau says, IIT and GWT are “so different that I don’t know how
to begin to compare them.” In contrast, Tagliazucchi thinks it possible
that the two are essentially the same theory, but “developed from third- and first-person viewpoints.”
The cognitive scientist Anil Seth
of the University of Sussex in the U.K. shares reservations about
whether the Templeton project might prove premature. A “definitive
rebuttal or validation” seems unlikely, he said, because the theories
“make too many different assumptions, have different relations to
testability and may even be trying to explain different things. GWT
seems mostly about function and cognitive access, while IIT is a theory
based primarily on phenomenology, not function, and is difficult to
test.”
Tononi and his collaborators would counter that they have been developing experimental tests of IIT for many years — work that has led to the development of a crude but effective tool for evaluating consciousness in brain-damaged patients.
Yet even Tononi agrees that, because both theories are still under
construction and remain so “far apart,” it might be too much to expect a
definite outcome. “Their predictions aren’t as precise as in physics,”
he said.
Still, he argues that “in the interests of making progress, you have
to start with what you’ve got.” Besides, the exercise “forces the
theories to say something specific.” Regardless of the outcome, Tononi
feels sure that the tests will teach us something new and useful about
the brain.
Other Contending Theories
No one imagines that eliminating GWT or IIT would solve the mystery
of what consciousness is. For one thing, there are other serious
theories, too.
Among them, two common classes are called first-order and
higher-order theories (HOTs). “A first-order theory says that there’s
nothing more to the mind than the basic cognitive processing of sensory
information,” according to Lau. What brings some of that sensory
information into consciousness, first-order theorists say, is something
unidentified but intrinsic to how it’s represented in the brain — for
example, the dynamics of the interactions among elements in its neural
network.
Lucy Reading-Ikkanda/Quanta Magazine
In contrast, he said, “higher-order theorists say that the mind does
something with the representation, over and above the cognition itself,
to produce consciousness.” In a HOT, a conscious experience is not
merely a record of the perceptions involved but involves some additional
mechanism that draws on that representation. That higher-order state
doesn’t necessarily serve some function in processing the information,
as in GWT; it just is.
“Compared to other existing theories, HOT can more readily account
for complex everyday experiences, such as emotions and episodic
memories,” Lau and his colleagues, the philosopher Richard Brown of LaGuardia Community College and the neuroscientist Joseph LeDoux of New York University, wrote recently.
The Templeton World Charity Foundation has assigned further funds to
test such ideas as it will GWT and IIT. “I hope to host about nine
meetings over the next five years, to bring together two or more
incompatible theories and try to hash it out between those theories,”
Potgieter said. He admits that “it might be that none of the current
ideas is correct.”
It may also turn out that no scientific experiment can be the sole
and final arbiter of a question like this one. “Even if only
neuroscientists adjudicated the question, the debate would be
philosophical,” Fallon said. “When interpretation gets this tricky, it
makes sense to open the conversation to philosophers. Many of the
neuroscientists in this field are already engaging in philosophy, some
quite excellently.”
Potgieter hopes that the adversarial approach will allow progress on
other big questions — like understanding how consciousness arose in the
first place, or how life itself did. “Wherever there is a big question
with a bunch of different theories that are all strong but all siloed
away from each other, we will try to make progress by breaking down the
silos,” he said.
“I think it is a wonderful initiative, and should be much more
frequent in science,” Tononi said. “It forces the proponents to focus
and enter some common framework. I think we all stand to gain one way or
another.”
