Synesthesia is one of those weird brain conditions that fascinates researchers and the public alike. For the uninitiated, synesthetes are people of sound mind and regular intelligence who, for reasons unknown, get their senses mixed up. They hear sounds when they read words, or see colours when they hear sounds. Or experience a change in temperature when they touch things. And so on: just about every possible combination of mixed-up senses has been reported by researchers who study synesthetes. But something about this work has always bugged me: how do the researchers know their subjects aren’t just making it up?

I talked to David Eagleman of the University of Texas earlier today and he explained that it’s all about consistency. He has studied hundreds of synesthetes and says that they always report the same kind of associations. If someone sees the colour green when they read the word Tuesday, then Tuesday will always be green for that person. It doesn’t matter how many words you ask them to link to colours, they will always link the two things in the same way.

He also says that around 1% of the populations are synthesthetes. So if you think you might be a synesthete, check out https://synesthete.org. Eagleman has put all his tests up there, and you can run them on yourself.

Synesthesia is one of those weird brain conditions that fascinates researchers and the public alike. For the uninitiated, synesthetes are people of sound mind and regular intelligence who, for reasons unknown, get their senses mixed up. They hear sounds when they read words, or see colours when they hear sounds. Or experience a change in temperature when they touch things. And so on: just about every possible combination of mixed-up senses has been reported by researchers who study synesthetes. But something about this work has always bugged me: how do the researchers know their subjects aren’t just making it up?

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