I have definitely seen film of babies displaying fear of heights, when placed on a glass sheet-
this instinct manifests itself so that the child does not have to fall or be dropped to know that falling is a Bad Thing.
Chimpanzees never exposed to snakes show an instinctive fear of them in the laboratory-
typically, this reaction doesn’t seem to be quite so hardwired in the human infant, and although it seems some infants are afraid of snakes, others are not.
Somehow, the preprogrammed parts of human behaviour seem to be transmitted as innate capacities, rather than full-blown instincts-
except, I would suggest, in the case of instinctive fear of heights.
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