I often wondered why I lusted over P F Chang's roast duck
James Loo
NMR Facility Director
UCSC
Santa Cruz, CA 95064
Moral judgments can be altered ... by magnets
By disrupting brain activity in a particular region, neuroscientists can
sway people's views of moral situations.
Anne Trafton, MIT News Office
To make moral judgments about other people, we often need to infer their
intentions --- an ability known as "theory of mind." For example, if one
hunter shoots another while on a hunting trip, we need to know what the
shooter was thinking: Was he secretly jealous, or did he mistake his
fellow hunter for an animal?
MIT neuroscientists have now shown they can influence those judgments by
interfering with activity in a specific brain region --- a finding that
helps reveal how the brain constructs morality.
Previous studies have shown that a brain region known as the right
temporo-parietal junction (TPJ) is highly active when we think about
other people's intentions, thoughts and beliefs. In the new study, the
researchers disrupted activity in the right TPJ by inducing a current in
the brain using a magnetic field applied to the scalp. They found that
the subjects' ability to make moral judgments that require an
understanding of other people's intentions --- for example, a failed
murder attempt --- was impaired.
The researchers, led by Rebecca Saxe, MIT assistant professor of brain
and cognitive sciences, report their findings
<
http://www.pnas.org/content/early/2010/03/11/0914826107.full.pdf+html>
in the /Proceedings of the National Academy of Sciences/ the week of
March 29. Funding for the research came from The National Center for
Research Resources, the MIND Institute, the Athinoula A. Martinos Center
for Biomedical Imaging
<
http://www.nmr.mgh.harvard.edu/martinos/aboutUs/index.php>, the Simons
Foundation <
http://sfari.org/> and the David and Lucille Packard Foundation.
The study offers "striking evidence" that the right TPJ, located at the
brain's surface above and behind the right ear, is critical for making
moral judgments, says Liane Young, lead author of the paper. It's also
startling, since under normal circumstances people are very confident
and consistent in these kinds of moral judgments, says Young, a
postdoctoral associate in MIT's Department of Brain and Cognitive Sciences.
"You think of morality as being a really high-level behavior," she says.
"To be able to apply (a magnetic field) to a specific brain region and
change people's moral judgments is really astonishing."
*Thinking of others*
Saxe first identified the right TPJ's role in theory of mind a decade
ago --- a discovery that was the subject of her MIT PhD thesis in 2003.
Since then, she has used functional magnetic resonance imaging (fMRI) to
show that the right TPJ is active when people are asked to make
judgments that require thinking about other people's intentions.
In the new study, the researchers wanted to go beyond fMRI experiments
to observe what would happen if they could actually disrupt activity in
the right TPJ. Their success marks a major step forward for the field of
moral neuroscience, says Walter Sinnott-Armstrong, professor of
philosophy at Duke University.
"Recent fMRI studies of moral judgment find fascinating correlations,
but Young et al usher in a new era by moving beyond correlation to
causation," says Sinnott-Armstrong, who was not involved in this research.
The researchers used a noninvasive technique known as transcranial
magnetic stimulation (TMS) to selectively interfere with brain activity
in the right TPJ. A magnetic field applied to a small area of the skull
creates weak electric currents that impede nearby brain cells' ability
to fire normally, but the effect is only temporary.
In one experiment, volunteers were exposed to TMS for 25 minutes before
taking a test in which they read a series of scenarios and made moral
judgments of characters' actions on a scale of one (absolutely
forbidden) to seven (absolutely permissible).
In a second experiment, TMS was applied in 500-milisecond bursts at the
moment when the subject was asked to make a moral judgment. For example,
subjects were asked to judge how permissible it is for a man to let his
girlfriend walk across a bridge he knows to be unsafe, even if she ends
up making it across safely. In such cases, a judgment based solely on
the outcome would hold the perpetrator morally blameless, even though it
appears he intended to do harm.
In both experiments, the researchers found that when the right TPJ was
disrupted, subjects were more likely to judge failed attempts to harm as
morally permissible. Therefore, the researchers believe that TMS
interfered with subjects' ability to interpret others' intentions,
forcing them to rely more on outcome information to make their judgments.
"It doesn't completely reverse people's moral judgments, it just biases
them," says Saxe.
When subjects received TMS to a brain region near the right TPJ, their
judgments were nearly identical to those of people who received no TMS
at all.
While understanding other people's intentions is critical to judging
them, it is just one piece of the puzzle. We also take into account the
person's desires, previous record and any external constraints, guided
by our own concepts of loyalty, fairness and integrity, says Saxe.
"Our moral judgments are not the result of a single process, even though
they feel like one uniform thing," she says. "It's actually a hodgepodge
of competing and conflicting judgments, all of which get jumbled into
what we call moral judgment."
Saxe's lab is now studying the role of theory of mind in judging
situations where the attempted harm was not a physical threat. The
researchers are also doing a study on the role of the right TPJ in
judgments of people who are morally lucky or unlucky. For example, a
drunk driver who hits and kills a pedestrian is unlucky, compared to an
equally drunk driver who makes it home safely, but the unlucky homicidal
driver tends to be judged more morally blameworthy.
Received on Tue Mar 30 2010 - 07:14:35 MST