A quirk in the way human brains process information means that when something becomes rare, we sometimes see it in more places than ever. A series of experiments show that people often respond to decreases in the prevalence of a stimulus by expanding their concept of it.

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A quirk in the way human brains process information means that when something becomes rare, we sometimes see it in more places than ever. A series of experiments show that people often respond to decreases in the prevalence of a stimulus by expanding their concept of it.