You have these gut reactions and they feel authoritative, like the voice of
God or your conscience. But these instincts are not commands from a higher
power. They are just emotions hardwired into the brain as we evolved.
the trolley. Is it right to push the man onto the
track below, killing him to save the ;ve, or is
the most moral move doing nothing at all?
“I was fascinated by the work of Foot and
Thompson,” Greene says, “because trolley
problems capture the central tension between
the two most dominant ideas in moral philosophy.” On the one hand, the philosophy
associated with Kant argues that morality is
about the rights and duties that all individuals have and about certain lines that must
not be crossed. Pushing the man from the
footbridge seems to cross one of those lines.
On the other hand, the utilitarianism of Mill
suggests that morality requires making the
hard choices to serve the greater good—even
if, on rare occasions, it can literally mean
throwing someone under the bus. Flipping
the switch appears to be a choice like that.
disruptions to personality, implicating other
centers of emotion. Damasio proposed that the
decision-making process, long deemed rooted
in reason, was guided by emotion as well.
“I bolted straight up and said, Aha! This
is it,” Greene recalls. “I think I actually cop-
ied the pages from the book and faxed them
to my adviser.” What people with this sort
of brain damage were missing was the gut
feeling that made other people cringe at
the thought of throwing a man in front of
a trolley, even as they felt it would be right
to throw the switch. Not so for the brain-
damaged patients, Greene surmised. “;ey
would be ;; with pushing the guy off the
footbridge; but in real life, in general, when
it came to feeling what was right rather than
reasoning it out, they would be stumped.”
By then a graduate student studying phi-
losophy at Princeton, Greene wrote a paper
called “;e Two Moralities.” Inside each of
us, he wrote, the theories of Kant and Mill
are constantly competing. Our minds are
not devotees of one moral code or the other.
We must always choose.
Suddenly Green saw morality not just as
a philosophical concept but as a neurological phenomenon. This was the beginning
of what he calls his dual-process theory of
moral judgment, in which instinct and reason collide in a battle for supremacy. The
grand ethical tension between Kant and Mill,
he hypothesized, was based on the tensions
between competing systems in the brain. “I
was studying traditional philosophy, but I felt
the real progress to be made in ethics was
in neuroscience,” Greene says.
Soon afterward, Greene found himself in
Israel for his sister’s bat mitzvah. To pass the
time in his Jerusalem hotel room, he picked
up a copy of Descartes’ Error, neuroscientist
Antonio Damasio’s pioneering book about
emotion in the brain. Damasio’s central narra-
tive involved the strange case of Phineas Gage,
a ;;th-century railroad construction foreman
whose skull was pierced by a metal spike dur-
ing an explosion. Gage was returned to health
by the ministrations of his doctor and seemed
physically recovered. But he was no longer
socially functional because his capacity to
make well-reasoned decisions and future plans
was deeply impaired. Damasio and his wife,
Hanna, a neurologist, studied Gage’s skull and,
on the basis of historical reports of his person-
ality decline, concluded that his problems had
resulted from damage to the ventromedial
prefrontal cortex, an area of the brain near the
center of the forehead that is associated with
emotion. They also studied contemporary
patients with brain damage causing similar
;;;;;;;; ; ;;; ;;;;;;, ;;;;;; ;;;;;;
the help of Jonathan Cohen, a Princeton neu-
roscientist studying how the brain coordi-
nates attention, thought, and action in pursuit
of a goal. One of Cohen’s main tools was func-
tional magnetic resonance imaging ( f;;;), the
same instrument Greene and Cushman used
to observe blood oxygen levels in different
regions of the brain.
As an advanced grad student and then a
postdoc in Cohen’s pioneering Neuroscience
of Cognitive Control Laboratory, Greene ;rst
began using f;;; to scan volunteers as they
considered trolley scenarios and other tough
philosophical problems. His landmark paper,
published in Science in ;;;;, was among
the first to document the brain structures
involved in moral choice. Subjects contem-
C
plating shoving a man to his death showed
heightened activity in the medial frontal
gyrus, the posterior cingulate gyrus, and the
angular gyrus, all centers of emotion and
social cognition in the brain. Subjects considering whether to pull a trolley switch showed
more activity in the dorsolateral prefrontal
cortex, a region tied to reasoning.
;e balance between those brain systems
could shift, Greene found, depending on an
individual’s degree of participation in the
intervention. If the onlooker imagined pushing the large man with his hands or a pole,
;; percent found it acceptable to throw him
in front of the trolley. Yet ;; percent said it
was ;; to pull a switch that would topple
him though a trapdoor and onto the tracks.
Two di;erent actions, same outcome.
“The main factor here is whether or not
we use personal force,” says Greene, who
points to historical and observational data
suggesting people have a reluctance to hurt
each other, even in times of war. “We seem
to have this general mechanism that makes
us reluctant to engage in physical violence,
and the mechanism is on autopilot. In this
very unusual case, our emotions don’t distin-
guish between gratuitous violence and acts
aimed at promoting the general good.”
Next Greene wondered if he could inten-
sify the conflict between the brain systems
simply by raising the stakes. ;e crying baby
dilemma, a frightening wartime drama, was
the perfect test. Greene asked volunteers to
imagine this: You are hiding with fellow villag-
ers in a basement while enemy soldiers search
for you. Suddenly your baby starts to cry, and
you cover its mouth to muffle the sound. If
the soldiers hear the baby, they will find all
the villagers, including you and your baby,
and kill everyone. But if you don’t move your
hand, the baby will smother to death. What is
the morally acceptable action?
“A good dilemma is one that makes you go
ugh,” Greene says. “If you ask if it’s ;; to feed
someone to a shark, that’s an easy negative.
In the best dilemmas, you have a strong emotional response competing with a compelling
utilitarian justi;cation. ;ey have to be nasty.”
