Instinct
Natural selection

The process by which Wundt explained the existence of instincts is natural selection. More specifically, his research suggests natural selection causes small changes in the nervous system over time. These changes bring about hereditary drives in organisms, which are then responsible for any unconscious processes. Another thing to note is that Wundt used the terms unconscious processes, reflexive movements, and instinctive movements interchangeably, often grouping them together.
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