cultural changes they may produce (and sooner than we think), given
the naturalistic turn in the image of humankind. I close by arguing that
ultimately we will need a new “ethics of consciousness.” If we arrive at a
comprehensive theory of consciousness, and if we develop ever more
sophisticated tools to alter the contents of subjective experience, we will
have to think hard about what a good state of consciousness is. We urgently
need fresh and convincing answers to questions like the following:
Which states of consciousness do we want our children to have?
Which states of consciousness do we want to foster, and which do we
want to ban on ethical grounds? Which states of consciousness can we
inflict upon animals, or upon machines? Obviously, I cannot provide definitive
answers to such questions; instead, the concluding chapters are
meant to draw attention to the important new discipline of neuroethics
while at the same time widening our perspective.
THE PHENOMENAL SELF-MODEL
Before I introduce the Ego Tunnel, the central metaphor that will guide
the discussion from here onward, it will be helpful to consider an experiment
that strongly suggests the purely experiential nature of the self. In
1998, University of Pittsburgh psychiatrists Matthew Botvinick and
Jonathan Cohen conducted a now-classic experiment in which healthy
subjects experienced an artificial limb as part of their own body. The
subjects observed a rubber hand lying on the desk in front of them, with
their own corresponding hand concealed from their view by a screen.
The visible rubber hand and the subject’s unseen hand were then synchronously
stroked with a probe. The experiment is easy to replicate:
After a certain time (sixty to ninety seconds, in my case), the famous
rubber-hand illusion emerges. Suddenly, you experience the rubber
hand as your own, and you feel the repeated strokes in this rubber hand.
Moreover, you feel a full-blown “virtual arm”—that is, a connection
from your shoulder to the fake hand on the table in front of you.
The most interesting feature I noticed when I underwent this experiment
was the strange tingling sensation in my shoulder shortly before the onset of the illusion—shortly before, as it were, my “soul arm” or “astral
limb” slipped from the invisible physical arm into the rubber hand. Of
course, there is no such thing as a ghostly arm, and probably no such thing
as an astral body, either. What you feel in the rubber-hand illusion is what
I call the content of the phenomenal self-model (PSM)—the conscious
model of the organism as a whole that is activated by the brain. (“Phenomenal”
is used here, and throughout, in the philosophical sense, as pertaining
to what is known purely experientially, through the way in which
things subjectively appear to you.) The content of the PSM is the Ego.
The PSM of Homo sapiens is probably one of nature’s best inventions.
It is an efficient way to allow a biological organism to consciously
conceive of itself (and others) as a whole. Thus it enables the organism
to interact with its internal world as well as with the external environ-ment in an intelligent and holistic manner. Most animals are conscious
to one degree or another, but their PSM is not the same as ours. Our
evolved type of conscious self-model is unique to the human brain, in
that by representing the process of representation itself, we can catch
ourselves—as Antonio Damasio would call it—in the act of knowing. We
mentally represent ourselves as representational systems, in phenomenological
real-time. This ability turned us into thinkers of thoughts and
readers of minds, and it allowed biological evolution to explode into cultural
evolution. The Ego is an extremely useful instrument—one that
has helped us understand one another through empathy and mindreading.
Finally, by allowing us to externalize our minds through cooperation
and culture, the Ego has enabled us to form complex societies.
What lessons can be learned from the rubber-hand illusion? The first
point is simple to understand: Whatever is part of your PSM, whatever
is part of your conscious Ego, is endowed with a feeling of “mineness,” a
conscious sense of ownership. It is experienced as your limb, your tactile
sensation, your feeling, your body, or your thought. But then there is a
deeper question: Isn’t there something more to the conscious self than
the mere subjective experience of ownership for body parts or mental
states? Isn’t there something like “global ownership,” a deeper sense of
selfhood having to do with owning and controlling your body as a
whole? What about the experience of identifying with it? Could this
deep sense of selfhood perhaps be experimentally manipulated? When I
first experienced the rubber-hand illusion, I immediately thought it
would be important to see whether this would also work with a whole
rubber body or an image of yourself. Could one create a full-body analog
of the rubber-hand illusion? Could the entire self be transposed to a location
outside of the body?
As a matter of fact, there are phenomenal states in which people have
the robust feeling of being outside their physical body—these are the socalled
out-of-body experiences, or OBEs. OBEs are a well-known class
of states in which one undergoes the highly realistic illusion of leaving
one’s physical body, usually in the form of an etheric double, and moving
outside of it. Phenomenologically, the subject of experience is located
in this double. Obviously, if one seriously wants to understand what the conscious self is, these experiences are of great philosophical
and scientific relevance. Could they be created in the lab?
One of the neuroscientists I am proud to collaborate with is Olaf
Blanke, a brilliant young neurologist at the Swiss Federal Institute of
Technology in Lausannne, who was the first scientist to trigger an OBE
by directly stimulating the brain of a patient with an electrode. There
are typically two representations of one’s body in these experiences: the
visual one (the sight of your own body, lying on the bed, say, or on an
operating table) and the felt one, in which you feel yourself to be hovering
above or floating in space. Interestingly, this second body-model is
the content of the PSM. This is where the Ego is. In a series of virtualreality
experiments, Olaf, his PhD student Bigna Lenggenhager, and I attempted
to create artificial OBEs and full-body illusions (see chapter 3).
During these illusions, subjects localized themselves outside their body
and transiently identified with a computer-generated, external image of
it. What these experiments demonstrate is that the deeper, holistic
sense of self is not a mystery immune to scientific exploration—it is a
form of conscious representational content, and it can be selectively manipulated
under carefully controlled experimental conditions.
Throughout the book, I use one central metaphor for conscious experience:
the “Ego Tunnel.” Conscious experience is like a tunnel. Modern
neuroscience has demonstrated that the content of our conscious
experience is not only an internal construct but also an extremely selective
way of representing information. This is why it is a tunnel: What we
see and hear, or what we feel and smell and taste, is only a small fraction
of what actually exists out there. Our conscious model of reality is a lowdimensional
projection of the inconceivably richer physical reality surrounding
and sustaining us. Our sensory organs are limited: They
evolved for reasons of survival, not for depicting the enormous wealth
and richness of reality in all its unfathomable depth. Therefore, the ongoing
process of conscious experience is not so much an image of reality
as a tunnel through reality.
Whenever our brains successfully pursue the ingenious strategy of
creating a unified and dynamic inner portrait of reality, we become con-scious.
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