SYNESTHESIA AS A WINDOW INTO THE NATURE
OF THOUGHT
In 1880 Francis Galton, a
cousin of Charles Darwin and a celebrated scientist himself, published a paper
in Nature on the intriguing phenomenon of synesthesia. Synesthesia, from
the Greek roots syn, meaning “together”, and aesthesis, or “perception”,
is a condition in which people experience the blending of two or more senses,
perhaps because two separate areas of the brain elicit activity in each other.
Even though scientists have known about synesthesia since Galton times, for
lacking in brain knowledge and subjective nature of the phenomenon, it has
often been considered as fakery, an
artifact of drug use or a mere
curiosity.
In the new millennium
beginning, Vilayanur Ramachandran, director of the Center for Brain and
Cognition at the University of California in San Diego and his fellow student
Edward Hubbard (now postdoctoral fellow at INSERM) among others, began to
uncover brain processes that could account for synesthesia (Psychophysical Investigations into the Neural Basis of
Synaesthesia. Proceedings of the Royal Society of London, B, 268, 979-983,
2001).
Perhaps one person in 200
experience the phenomenon, which can occur in about 50 different types. In a
common form of synesthesia, looking at a number can evoke a colour. It has been
demonstrated that brain areas that normally don’t interact when processing
numbers or colours do activate one another in synesthesia (Hubbard et al., Individual Differences among Grapheme-Color Synesthetes:
Brain-Behaviour Correlations. Neuron 45 (6), 975-985, 2005). In one rare kind each letter is associated with male or female
sex.
Synestesia is much more
common in creative people than in the general population, and it seems more
frequent in women than men. As the condition runs in families, neurogenetic
studies might provide relevant insights into molecular differences from normal
people.
Studying mechanisms
involved in synesthesia Ramachandran, Hubbard and their colleagues are also
learning about how the brain in general processes sensory information and uses
it to make abstract connections between seemingly unrelated inputs. For that
they consider synesthesia a window into the nature of thought.