Is it true that rats laugh when tickled? - briefly
Rats produce ultrasonic vocalizations that researchers interpret as a form of laughter when they are tickled. These sounds occur at frequencies above human hearing and are associated with positive affect.
Is it true that rats laugh when tickled? - in detail
Rats produce ultrasonic vocalizations (USVs) in the 50‑80 kHz range when their bodies are gently stroked or ticked. These sounds differ from the broadband calls associated with distress and have been linked to positive affective states.
The emissions meet three criteria commonly used to define laughter in non‑human animals:
- Spontaneity – USVs appear without prior conditioning during light tactile stimulation.
- Acoustic pattern – Calls are short, frequency‑modulated bursts that repeat at a rate of 4‑7 Hz, resembling the rhythmic structure of human giggling.
- Contextual association – The vocalizations occur alongside increased dopamine release in the nucleus accumbens and exploratory behavior, indicating reward processing.
Experimental evidence supports this interpretation. In a 2011 study, rats exposed to a soft brush emitted USVs at an average of 0.8 calls s⁻¹, while control animals showed no such activity. Subsequent recordings demonstrated that the same rats produced fewer calls after administration of dopamine antagonists, confirming a neurochemical link to positive affect.
Physiological responses accompany the vocal output. Heart rate measurements reveal a transient reduction during tickling, mirroring parasympathetic activation observed in human laughter. Additionally, facial muscles, particularly the whisker pads, display rhythmic contractions synchronized with the ultrasonic bursts.
These findings suggest that rats possess a laughter‑like response to tactile play. The behavior satisfies behavioral, acoustic, and neurochemical benchmarks for laughter, providing a robust model for studying the evolution of humor and social bonding in mammals.