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Writing & language

Peter Wason’s verbal illusion

Illusions are not just visual. Our verbal cognitive processes can be tricked too.

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Illusions are not just visual. Our verbal cognitive processes can be tricked too.

A sentence that reads "No head injury is too trivial to be ignored"

Psychologist Peter Wason1 observed that this sentence is almost universally misread. Taken literally it means we should ignore all head injuries. But because we know this is not what is intended, we disregard the literal meaning and assume it is saying that ‘No head injury is too trivial to be treated’. This is an example of a verbal illusion.

This is also an example of how easy it is to misunderstand negative sentences. Better to rephrase it as ‘All head injuries should be treated, however trivial’.

And if you really do mean to make a point that appears to go against common sense or established knowledge, take special care to spell this out, rather than set traps for your reader to trip on. That would be a dark pattern.

1. Wason, P. C., & Reich, S. S. (1979). A Verbal Illusion. Quarterly Journal of Experimental Psychology, 31(4), 591-597.

How this helps
Avoid expressing crucial information using a negative sentence construction.
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