This one has possibilities, but I am restrained. Scientists have discovered that rats
enjoy being tickled. "The rats likely keep their chuckles to supersonic levels to avoid detection by potential predators," but researchers heard their laughter via an ultrasonic detector. But, you tickle, they laugh, and come back for more. Inevitably, more of made of this than the humor of it; evolution, chimps, then human males and females (is one really just flirting?), the need for anti-depressants, etc. "What seems to be special about humans is the variety of laughter sounds we produce and how we seem to alter that sound, depending on the social situation," said a scientist. For us humans, laughter is a social tool, not just an expression of joy, they say. They’ve never heard me laugh...