May
26, 2005
Grasping Metaphors:
UCSD Research Ties Brain Area To Figures Of Speech
By Inga Kiderra
What does it take to
fathom a proverb – catch the figurative meaning of “an
apple doesn’t fall far from the tree”?
According to research
led by V. S. Ramachandran, director of the Center for Brain
and Cognition at the University of California, San Diego, a
region of the brain known as the angular gyrus is probably at
least partly responsible for the human ability to understand
metaphor.
|
The
angular gyrus region of the brain
Courtesy
of Center for Brain and Cognition, University
of California, San Diego |
|
|
Ramachandran and colleagues
tested four right-handed patients with damage to the left angular
gyrus. Fluent in English and otherwise intelligent and mentally
lucid, the patients showed gross deficits in comprehending such
common proverbs as “the grass is always greener on the
other side” and “an empty vessel makes more noise.”
Asked to explain the sayings, the patients tended give responses
that were literal. The metaphorical meaning escaped them almost
entirely.
When pressed to provide
deeper or more general accounts, Ramachandran said, “the
patients often came up with elaborate, even ingenious interpretations
– that were completely off the mark.”
Patient SJ, for example,
a former physician who could maintain the flow of normal conversation
and even retained the ability to correctly diagnose descriptions
of symptoms, got all 20 of the 20 proverbs he was tested on
wrong. Prodded on “all that glitters is not gold,”
he finally said that it meant you had to be very careful when
buying jewelry because you might get robbed.
The patients were equally
bad at matching a bulbous, amoeboid shape to the sound “booba”
and a jagged shape to “kiki.” (See figure.) Whereas
more than 90 percent of ordinary respondents succeed at this
task – of translating one sort of sensory information
into another – patients with damage to the angular gyrus
performed at the level of chance.
|
The
“Booba/Kiki” naming task: More than 90
percent of normal respondents will match the non-word
“booba” to the curvy shape at left and
“kiki” to the geometric shape at right.
Study subjects with damage to the angular gyrus, however,
performed at the level of chance. V.S. Ramachandran
believes this supports the idea that the angular gyrus
– which lies at the crossroads of brain regions
specialized for vision, hearing and touch –
is critical to translating between the different “languages”
of our senses and plays an important role in metaphorical
thinking.
Courtesy of
Center for Brain and Cognition, University of California,
San Diego |
|
Three age-matched control
subjects, on the other hand, with lesions in other areas of
the brain, performed normally both with proverbs and the booba/kiki
test.
Disproportionately
larger in hominids than other primates, the angular gyrus, given
its strategic location at the crossroads of areas specialized
for processing touch, hearing and vision, Ramachandran conjectures,
is critical both to conceptual metaphors and to cross-modal
abstractions more generally.
“While it would
be premature to conclude that the angular gyrus is the ‘metaphor
center’ of the human brain, we suggest that the evolution
of the dominant angular gyrus contributed enormously to the
evolution of many quintessentially human abilities, including
metaphorical – and other abstract – thinking,”
Ramachandran said.
“Any monkey can
reach for a peanut,” he said, “but only a human
can reach for the stars or even understand what that means.”
Ramachandran’s
lab is continuing work on linking other brain areas, the supramarginal
gyrus and human homologues of mirror neurons, for example, to
other types of metaphoric abilities.
Intriguingly, in the
current study, patient KK, who had damage not only to the angular
gyrus but also to the supramarginal gyrus, was abysmal at understanding
action metaphors such as “grasping an idea” or “putting
your finger on the main argument.”
Presented at the American
Psychological Society annual convention in Los Angeles, May
26-29, the research is supported by grants from the Kavli Foundation,
the Mind Science Foundation and R. Geckler.
Media Contact: Inga
Kiderra, (858) 822-0661
|