Synaesthesia is a mixing of senses and perception, so that, for instance, the number 9 is associated with the colour orange, or France with the taste of apples. Researchers from the University of Edinburgh tested 615 children, aged six-seven at 21 UK schools for a particular kind of synaesthesia where numbers are linked to colours. The researchers found that 1.3% of the children had this form of synaesthesia. The colour associated with each number remained constant over time and more links were added as the children grew up. The average child with synaesthesia had 10.5 number-colour links when aged six-seven and 16.9 links a year later.
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