The important thing to note is that the uncanny valley is a hypothesis. There is some evidence that it might just be a modern cultural phenomenon or a collection of unrelated phenomena that is incorrectly classed together.
Also because it’s just a hypothesis we don’t know what causes it or exactly why it happens. The top leading theories are that we react strongly to things that are “slightly” off because it helps us avoid disease or because it “threatens our idea of human identity”.
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