Such people are known as synaesthetes, and the phenomenon of synaesthesia has puzzled brain scientists since it was recognised over a century ago.
我们把这类人称为联觉者，自从联觉现象被人类所认识以来，它已经困扰了人脑科学家们长达一个多世纪之久。
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Most researchers in the field suspect synaesthesia is caused by crossed wires in synaesthetes' brains, but until recently they have had no way to check this hypothesis.