Who Needs Emotions? The Brain Meets the Robot

how do we decipher others’ minds? 157
THE CONCEPT OF SHARED REPRESENTATIONS:
A NEURAL BASIS FOR THE SIMULATION THEORY
Little is known of the biological effects of observing someone’s actions and
emotions. However, extending the simulation theory to understanding the
representations underlying actions and emotions of other people requires that
a continuity be established between the embodiment of representations of
the observer and those of the agent being observed.
Consider a simple experiment with normal subjects observing the action
of an actor. The subjects, equipped for recording their respiration rate, sit in
front of a large screen on which they see an actor performing an effortful action.
The actor stands on a treadmill that either is motionless, moves at a constant
velocity (2.5, 7, or 10 km/h), or progressively accelerates from 0 to
10 km/h over 1 minute. The main result of this experiment (Paccalin &
Jeannerod, 2000) is that the respiration rate increased during the observation
of the actor walking or running at an increasing speed. Typically, the average
increase during observation of the actor running at 10 km/h is about 25% above
the resting level. Further, the increase in respiration frequency correlates with
running velocity. Watching an action is thus different from watching a visual
scene with moving objects. While watching an action, the observer is not only
seeing visual motion but also internally (and nonconsciously) simulating (or
rehearsing) the action. Simulating accelerated running implies an increase in
the breathing rate because, if the running movements were actually executed,
they would require an anticipatory increase in metabolic needs. This finding
thus substantiates the hypothesis that perceiving an action triggers a neural
state where the neural structures potentially involved in executing that action
are facilitated (see details below).
Now, consider a similar experiment using the same paradigm of observation
of an actor. However, instead of performing a neutral action like running,
the actor displays an emotional state. Imagine an observer in front of a
screen, watching the actor’s face display different degrees of an emotion, like
joy. Joy would be expressed on that face by a set of expressions ranging from
a subtle smile to excitation and laughing. Also imagine that vegetative indices
(e.g., heart rate, galvanic skin response, breathing) are recorded from the
observer. What would be the conclusion to be drawn from that experiment
if, say, the respiration rate or the heart rate of the observer increased as a
function of the degree of joy expressed by the face of the actor? According
to the conclusion drawn from the action observation experiment, the conclusion
here should be that the observer is simulating the emotion displayed
by the actor and that this simulated emotion activates his or her own vegetative
system to the same extent as when actually experiencing the emotion.
Although this particular experiment may not have been performed (but