Rats laugh when they are tickled
Rats emit ultrasonic chirps near 50 kilohertz during play and tickling. The calls track reward and approach.
Established2 min read
Panksepp recorded 50 kHz vocalisations when rats wrestled and when a familiar hand tickled them. They ran toward the tickling hand. Aversive events produce a different call, near 22 kHz.
Calling it laughter is an analogy with a measurement under it. The calls are social, positive, and suppressed by fear. A species we treat as silent has been commenting, in ultrasound, the whole time.
Caveats
- You cannot hear it without a detector.
- The homology with human laughter is about state, not about the sound matching a giggle.
Sources
- 1Panksepp J., Burgdorf J.. ‘Laughing’ Rats and the Evolutionary Antecedents of Human Joy?. Physiology & Behavior 79, 2003.