Is it true that rats laugh? - briefly
When tickled, rats emit ultrasonic chirps that scientists describe as laughter‑like vocalizations. These sounds lie beyond human hearing and are detectable only with specialized equipment.
Is it true that rats laugh? - in detail
Research on rodent vocalisation shows that rats emit ultrasonic sounds when engaged in social play. These emissions occur at frequencies above human hearing range (approximately 22–50 kHz) and are temporally linked to playful behaviours such as chasing, pinning, and tickling. Experiments using gentle tactile stimulation—commonly referred to as “tickling”—induce a marked increase in the rate of these high‑frequency calls, suggesting a positive affective state.
Key observations from controlled studies include:
- Frequency range: 22–50 kHz, beyond audible spectrum for humans.
- Call pattern: Short bursts lasting 30–100 ms, often repeated in rapid succession.
- Behavioural context: Predominantly observed during rough‑and‑tumble play, after exposure to pleasant tactile cues, and during anticipation of reward.
- Physiological correlates: Elevated dopamine release in the nucleus accumbens and increased heart‑rate variability, both markers of positive emotional arousal.
Neurobiological investigations reveal that the emission of these ultrasonic vocalisations depends on the limbic system, particularly the amygdala and the ventral tegmental area. Pharmacological blockade of opioid receptors reduces call frequency, indicating that endogenous opioid signalling contributes to the affective component of the vocal response.
Comparative analysis with other mammals shows parallels to human laughter. In primates, laughter manifests as audible vocal bursts during play; in rats, the analogous response is ultrasonic. While the acoustic properties differ, the functional role—signalling a non‑threatening, rewarding social interaction—appears conserved.
The term “laugh” is therefore applied metaphorically to describe this phenomenon. Scientific literature frequently refers to the rat calls as “laughter‑like ultrasonic vocalisations» when discussing affective communication. Direct evidence for a conscious experience comparable to human mirth remains unavailable, but the convergence of behavioural, neurochemical, and physiological data supports the interpretation that rats produce a laughter‑analog during positive social encounters.