Thinking and Deciding

METHODS FOR EMPIRICAL RESEARCH 45
Physiological measurements
Although Aristotle thought that the brain was a fairly useless organ, we now know
that it, and the nerves coming out of it, are necessary for thinking, emotion, judgments,
and decisions. Today researchers are excited about the possibility of learning
just how the nervous system works to do these things. The immediate cause of the excitement
is the development of new methods for observation of brain activity while it
is going on, in “real time.” One such method is functional magnetic resonance imaging,
fMRI, which uses powerful magnets to measure blood flow in different regions
of the brain. The assumption is that blood flow increases when a part of the brain is
active.
An example of the use of fMRI in research on judgment is a study by Greene et
al. (2001). Subjects answered questions about moral dilemmas, such as whether it
is appropriate to push a man off a bridge in order to prevent a runaway trolley from
killing five other people, or whether it is appropriate to switch a runaway trolley
from a track where it will kill five to a track where it will kill one. Although both
versions involve killing one to save five, most people think that switching the trolley
is acceptable and pushing the man is not. Greene and his co-workers found that the
less acceptable version, and others like it, led to brain activity in regions that they
thought were related to emotion. This and other evidence led them to conclude that
the resistance to pushing was the result of an emotional reaction to the idea of it.
Several questions can be raised about this kind of research, as exemplified by this
study. First, we think that the brain areas are associated with emotion because they
are associated with other indicators of emotion, such as facial expression and verbal
reports. In many cases, we can rely directly on these other indicators and thus avoid
making an inference that may be incorrect. This is not always true: It may turn out,
for example, that fMRI is useful for lie detection or for detection of emotional states
that people are unwilling to report. But, if we just want to know whether people are
feeling emotion, there are less expensive ways to find out. Aside from asking them,
we can also use other physiological measures that are easier to get, such as increased
heart rate, respiration, or electrical signals from the skin on the palms that result from
sweat production.
Second, the knowledge of where something happens in the brain may be useful
for some purposes, but it does not directly lead to a psychological explanation.
People seem to have a tendency to think that a truly “scientific” explanation of judgments
and decisions will involve explaining how it all works in the brain. This idea
is called “reductionism.” It is an issue in many sciences. Biology can be partly explained
in terms of chemistry, and chemistry, in turn, in terms of physics. The most
naive version of reductionism holds that, in the distant future, the only science left
will be physics, and it will explain everything.
Baseball follows the laws of physics. The ball rises and falls in the shape of a
parabola (slightly distorted by predictable effects of wind and spin); the pitcher’s
hand obeys the laws of friction; and so on. But, no matter how much physical detail
we provide, we cannot understand baseball this way. To understand baseball, we