Do rats laugh when they are tickled? - briefly
Rats produce high‑frequency ultrasonic vocalizations when tickled, which researchers interpret as a form of laughter. These calls, typically around 50 kHz, intensify with stronger tickling stimuli.
Do rats laugh when they are tickled? - in detail
Research on rodents shows that when a rat’s belly or forelimbs are gently brushed, the animal produces ultrasonic vocalizations (USVs) in the 50‑80 kHz range. These high‑frequency sounds are not audible to humans but can be recorded with specialized microphones. The emission of USVs increases markedly during brief periods of tactile stimulation, indicating a positive affective response.
Key observations from controlled experiments:
- Stimulus protocol – Light strokes applied with a fine brush for 2–3 seconds, repeated at intervals of 10 seconds, reliably elicit vocal bursts.
- Acoustic profile – Calls consist of short, broadband chirps lasting 10‑30 ms, with peak frequencies around 70 kHz and amplitudes of 70‑80 dB SPL at the microphone.
- Physiological correlates – Simultaneous recordings show elevated heart rate variability and increased dopamine release in the nucleus accumbens, both markers of reward processing.
- Pharmacological manipulation – Administration of opioid antagonists (e.g., naloxone) reduces call frequency, linking the response to endogenous opioid signaling.
- Comparative context – Similar USVs are observed during play and social grooming, suggesting that the vocalization functions as a social “laugh” analogue rather than a reflexive distress signal.
Interpretation of these data supports the conclusion that rats exhibit a laughter‑like behavior when subjected to gentle tickling. The ultrasonic calls serve as an affective communication signal, facilitating social bonding among conspecifics. While the acoustic signature differs from human laughter in frequency and modality, the underlying emotional state—positive, reward‑driven arousal—is comparable.
Future directions include mapping neural circuits that generate the vocal response, testing the effect of environmental enrichment on call prevalence, and exploring cross‑species perception of these USVs by other mammals.