Neuroscientist Jaak Panksepp first heard rat "laughter" when he observed rats at play. In the late 1990s, he and his team tried to elicit the same laughing sounds by tickling the rats with their hands. They found that the rats seemed to enjoy and seek out the tickling treatment. Rat laughter sounds at about 50 kilohertz, so scientists need special machinery to hear the high-pitched chirps. According to Panksepp, the best way to tickle a rat is to start at the backs of their necks, then flip them over and tickle their bellies. Laughing in response to tickling is called gargalesis, and is also observable in great apes.
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Key Facts In This Video
Rat "laughter" sounds at 50 kilohertz. (0:47)
Rats seem to display empathy. One rat will try to free one another from a trap even if the two rats have never interacted before. (2:13)
95% of all lab animals are mice and rats. (3:12)