679 - The Brain - Supersenses

Supersenses

WHILE most of us have three types of colour receptors in our eyes, some people have four. This gives them an extra dimension to their colour perception. All these so-called tetrachromats are women, because the genes involved are on the X chromosomes. One person studied was an interior decorator, and was sensitive to colours within the range most people would see as just beige - so perhaps this supersense isn't always an advantage.

Then there are super-tasters, whose enhanced taste comes from having more than the average number of tastebuds. And acute hearing is common to most young adults, who can hear frequencies up to 20,000 hertz as compared with 8000 in the elderly. However, there is nothing special about the brains of supersensors. The human sensory cortex seems to be able to handle whatever information the sense organs can throw at it - the limits are down to the information coming in, not the grey matter that handles it.

But there is one way that the brain itself seems to stretch the boundaries of the sensors in a condition known as synaesthesia. Here the sensory experiences merge, as one sensation recruits others. Some people experience colours when they hear certain sounds or see words and numbers. Others hear sounds with touch sensations, or experience shapes with tastes. One theory for why this happens is heightened connectivity between different sensory areas in the brain.

Chromosome 2