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Emotional responses, such as fear of spiders, snakes, and heights, may have evolved to protect us from danger (Plomin, DeFries, Knopik, & Neiderhiser, 2013). Avoiding harmful creatures and precarious drop-offs would tend to increase the chances of survival, particularly for our primitive ancestors living in the wild. But when such fears become excessive and irrational, a specific phobia might be present.

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