Scientists are studying synaesthesia to understand how the human brain works. Different areas of the brain handle information from different senses. What mixes the senses up in the brains of people with synaesthesia? It may be that as newborn babies we all experience synaesthesia, but that by the age of four months the senses have been 'wired-up' to the correct parts of the brain. Perhaps people with synaesthesia have some 'cross-wiring' left over from this process.