Rat

The rat is a medium-sized rodent found almost everywhere humans live. Rats laugh when they are tickled. The sound is a high-pitched chirp, too high for human ears, which researchers recorded with special equipment in the 1990s and 2000s. Tickled rats come back for more and seek out the hand that tickled them.^[1] It is the only laboratory finding that required a scientist to tickle rats professionally for several years.

Hide-and-seek

In a 2019 study, rats were taught to play hide-and-seek with researchers in a room containing boxes. The rats learned to both hide and seek, waited in a starting box until it was their turn, and chose better hiding places when they were the ones hiding.^[2] They also laughed during the game, especially when found, and sometimes ran off to hide again, apparently to prolong it. The rats were not rewarded with food; they were rewarded with tickling.

The researchers report that the rats were better at the rules than many children, and more gracious when found.

Laughter

Rats also chirp when playing with each other. Young rats play-fight and chirp the most. A rat that has been tickled, then sees the tickler's hand again, starts chirping in advance, which is also how people react to a friend with a known joke and a long queue to tell it in.

See also

• Cat – a traditional rival
• Echo – another sound you can't always hear properly
• Queue – something rats also understand
• Squirrel – a rat with better marketing

References

1. Tickle, T. (2003). Professional Tickling. Whisker Press.
2. Seek, H. & Hide, S. (2019). “Found You”. Play Science 1: 1.
3. Chirp, C. (1999). “Too High to Hear”. Ultrasound Quarterly 50: 1.