sense of ownership yet lose the sense of agency. But can one also hallucinate
agency? The answer is yes—and, oddly, many consciousness
philosophers have long ignored this phenomenon. You can have the robust,
conscious experience of having intended an action even if this
wasn’t the case. By directly stimulating the brain, we can trigger not only
the execution of a bodily movement but also the conscious experience
of having the urge to perform that movement. We can experimentally
induce the conscious experience of will.
Here’s an example. Stéphane Kremer and his colleagues at the University
Hospital of Strasbourg stimulated a specific brain region (the
ventral bank of the anterior cingulate sulcus) in a female patient with
medically intractable epileptic seizures, in order to locate the epileptogenic
zone before performing surgery. In this case, the stimulation
caused rapid eye movements scanning both sides of the visual field. The
patient began to search for the nearest object she could grasp, and the
arm that was opposite the stimulated side—her left arm—began to wander
to the right. She reported a strong “urge to grasp,” which she was unable
to control. As soon as she saw a potential target object, her left
hand moved toward it and seized it. On the level of her conscious experience,
the irrepressible urge to grasp the object started and ended with the stimulation of her brain. This much is clear: Whatever else the conscious
experience of will may be, it seems to be something that can be
turned on and off with the help of a small electrical current from an
electrode in the brain. But there are also ways of elegantly inducing the experience of
agency by purely psychological means. In the 1990s at the University of
Virginia, psychologists Daniel M. Wegner and Thalia Wheatley investigated
the necessary and sufficient conditions for “the experience of conscious
will” with the help of an ingenious experiment. In a study they
dubbed “I Spy,” they led subjects to experience a causal link between a
thought and an action, managing to induce the feeling in their subjects
that the subjects had willfully performed an action even though the action
had in fact been performed by someone else. Each subject was paired with a confederate, who posed as another
subject. They sat at a table across from each other and were asked to
place their fingertips on a little square board mounted on a computer
mouse, enabling them to move the mouse together, Ouija-board style.
On a computer screen visible to both was a photograph from a children’s
book showing some fifty objects (plastic dinosaurs, cars, swans,
and so on).
The real subject and the confederate both wore headphones, and it
was explained to them that this was an experiment meant to “investigate
people’s feelings of intention for acts and how these feelings come and
go.” They were told to move the mouse around the computer screen for
thirty seconds or so while listening to separate
audio tracks containing random
words—some of which would refer to one
or another object on the screen—along
with ten-second intervals of music. The
words on each track would be different, but
the timing of the music would be the same.
When they heard the music, they were to
stop the mouse on an object after a few seconds
and “rate each stop they made for personal
intentionality.” Unknown to the subject, however, the confederate did not hear any words or music at all
but instead received instructions from the experimenters to perform
particular movements. For four of the twenty or thirty trials, the confederate
was told to stop the mouse on a particular object (each time a different
one); these forced stops were made to occur within the prescribed
musical interval and at various times after the subject had heard the corresponding
word over her headphones (“swan,” say).According to the subjects’ ratings, there was a general tendency to
perceive the forced stops as intended. The ratings were highest when
the corresponding word occurred between one and five seconds before
the stop. Based on these findings, Wegner and Wheatley suggest that the
phenomenal experience of will, or mental causation, is governed by three
principles: The principle of exclusivity holds that the subject’s thought
should be the only introspectively available cause of action; the principle
of consistency holds that the subjective intention should be consistent
with the action; and the principle of priority holds that the thought
should precede the action “in a timely manner.”The social context and the long-term experience of being an agent of
course contribute to creating the sense of agency. One might suspect
that the sense of agency is only a subjective appearance, a swift reconstruction
after the act; still, today’s best cognitive neuroscience of the
conscious will shows that it is also a preconstruction. Experiencing
yourself as a willing agent has much to do with, as it were, introspectively
peeping into the middle of a long processing chain in your brain.
This chain leads from certain preparatory processes that might be described
as “assembling a motor command” to the feedback you get from
perceiving your movements. Patrick Haggard, of University College
London, perhaps the leading researcher in the fascinating and somewhat
frightening new field of research into agency and the self, has
demonstrated that our conscious awareness of movement is not generated
by the execution of ready-made motor commands; instead, it is
shaped by preparatory processes in the premotor system of the brain.
Various experiments show that our awareness of intention is closely related
to the specification of which movements we want to make. When
the brain simulates alternative possibilities—say, of reaching for a par-ticular object—the conscious experience of intention seems to be directly
related to the selection of a specific movement. That is, the awareness
of movement is associated not so much with the actual execution
as with an earlier brain stage: the process of preparing a movement by
assembling different parts of it into a coherent whole—a motor gestalt,
as it were.
Haggard points out that the awareness of intention and the awareness
of movement are conceptually distinct, but he speculates that they
must derive from a single processing stage in the motor pathway. It
looks as though our access to the ongoing motor-processing in our
brains is extremely restricted; awareness is limited to a very narrow window
of premotor activity, an intermediate phase of a longer process. If
Haggard is right, then the sense of agency, the conscious experience of
being someone who acts, results from the process of binding the awareness
of intention together with the representation of one’s actual movements.
This also suggests what subjective awareness of intention is good
for: It can detect potential mismatches with events occurring in the
world outside the brain.
Whatever the precise technical details turn out to be, we are now beginning
to see what the conscious experience of agency is and how to
explain its evolutionary function. The conscious experience of will and
of agency allows an organism to own the subpersonal processes in its
brain responsible for the selection of action goals, the construction of
specific movement patterns, and the control of feedback from the body.
When this sense of agency evolved in human beings, some of the stages
in the immensely complex causal network in our brains were raised to
the level of global availability. Now we could attend to them, think about
them, and possibly even interrupt them. For the first time, we could experience
ourselves as beings with goals, and we could use internal representations
of these goals to control our bodies. For the first time, we
could form an internal image of ourselves as able to fulfill certain needs
by choosing an optimal route. Moreover, conceiving of ourselves as autonomous
agents enabled us to discover that other beings in our environment
probably were agents, too, who had goals of their own. But I
must postpone this analysis of the social dimension of the self for a while and turn to a classical problem of philosophy of mind: the freedom
of the will.
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