If you tickle a rat's belly, it squeals with laughter. However, we are unable to perceive this laughter as its frequency, around 50 kHz, exceeds the range of human hearing. Neuroscientist Jaak ...

In fact, when they were tickled, laughter from both apes and humans was isochronous, meaning that the laughs followed a rhythmic pattern. In other words, the same amount of time passed between each ...