HOW MANY SENSES DO WE HAVE?

Science now challenges our common sense notions about our five senses. It seems that our five senses are not really separate. The job of one of them can be done by another. This has to do with the fascinating phenomenon of "synesthesia".

In school if not before, every child learns that there are five senses: Sight, smell, hearing, taste, and touch. And each sense is separate and relates to a particular body organ. We hear sounds with our ears and see sights with our eyes--never vice versa. We learn that our senses are distinct, individual, and completely independent of each other.

Most importantly, we are taught that a sensory organ cannot do double time. For instance, we cannot see sounds, hear sights, or touch tastes.

But research into synesthesia demonstrates otherwise.

Synesthesia refers to the process where an individual experiences "confusion" of senses. It's as if one or more sense merges with another. Sounds are seen, sights are heard, and tastes are touched.

Strong evidence exists that we are all synesthetes as newborns. We are born with our five senses all blurry and mixed together. It is only as we mature that our sensory organs become more specialized. For instance, our eyes have sensory channels which send information to and from the brain. In infancy, these channels are immature and send different sorts of signals compared to those sent when we're adults. The channels fully develop as our brain fully develops.

Research shows that the hearing of a sleeping newborn does not shut down in the same way that hearing is less acute when an adult is sleeping. In fact, brain wave experiments prove that a sleeping baby hears with their ears just as well when sleeping as when awake. With adults, the brain wave patterns differ and hearing is not nearly as good during sleep.

One study demonstrating infant synesthesia was conducted by Drs. David Lewkowicz and Gerald Turkewitz, from the Albert Einstein College of Medicine in New York. They discovered that babies between 3 and 4 weeks of age "equate brighter lights with louder sounds"--something adults definitely don't do.

In the experiment, Drs. Lewkowicz and Turkewitz first asked adults to attempt to adjust the volume of a loudspeaker to make it equal to the brilliance of a flashing light. The adults agreed remarkably well on the level of noise that seemed to equal the intensity of the light. Next, twenty infants were repeatedly exposed to the light while their pulse was monitored. A burst of noise was then substituted for one of the flashes. Although the level of noise that the adults had decided was equivalent to the light caused little reaction, every other level caused a marked quickening of each infant's pulse. And the quickening was proportionate to the difference between the intensity of the light and that of the matching sound. Thus, to a baby, brighter lights and louder sounds go together.

Although we all were synesthetes as babies, only a very few of us remain so into adulthood, perhaps one in 160,000. When Dr. Simon Baron-Cohen of London University spoke about synesthesia on Radio 4 in the U.K., over 200 people contacted the program. Most claimed they were synesthetes. When the "11AM" program recently interviewed a Sydney synesthete, calls came in to Channel 7 from all around Australia. Many said things like, "That's me. I've been like that all my life. I'm not crazy. Now I have a name for it and can talk about it."

Synesthetes tend to follow artistic careers. Many are painters and musicians. This is undoubtedly because their sensory abilities make them see the world far differently.

Since synesthesia research is just beginning, many questions remain. For example, can we learn to recapture in adulthood our previous synesthesia state in infancy? Could we ever be taught to see without eyes or hear without ears by drawing upon our other senses?

Dr. Richard Cytowic, a neurologist in Washington, D.C., thinks that this just might be possible. Dr. Cytowic is the author of the two best known books on adult synesthesia, Synesthesia: A Union Of The Senses and The Man Who Tasted Shapes. He has proven that the Russian composer Nikolai Rimsky-Korsakov and many other historical figures were synesthetes. He has seen over forty synesthetes in his practice. The sensory world of his patients is one of salty visions, purple odours, square tastes, and green wavy symphonies.

One of Dr. Cytowic's patients even allegedly has technicolour orgasms.

Dr. Cytowic believes that understanding synesthesia will provide a key towards understanding the human mind.

What is the most common form of synesthesia? This seems to be "colour-hearing" according to Dr. Baron-Cohen. Such colour-hearing synesthetes nearly always have "coloured vowels" and "coloured letters".

So it seems that yesterday's common sense about sense may be nonsense.

Further Reading:

Cytowic, R. The Man Who Tasted Shapes. Cambridge, Mass.: MIT Press. 1998.
Nunn JA, Gregory LJ, Brammer M, Williams SC, Parslow DM, Morgan MJ, Morris RG, Bullmore ET, Baron-Cohen S, Gray JA. Functional magnetic resonance Imaging of synesthesia: activation of V4/V8 by spoken words. Nat Neurosci. 2002 Apr;5(4):371-5.
Smilek D, Dixon MJ, Cudahy C, Merikle PM. Concept driven color experiences in digit-color synesthesia. Brain Cognition 2002 Mar-Apr;48(2-3):570-3.

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