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When rats engage in play behavior or are tickled by a human, they emit a sound which can only be picked up by special microphones.
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Baby chimpanzees, gorillas, and orangutans also make distinct, laughter-like vocalizations when tickled by humans.
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The infamously mischievous kea parrot of New Zealand doesn’t exactly laugh, but it does produce a special “play call” which triggers play behavior in other keas — like infectious laughter.
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