The Mystery of the Feline Purr: A New Perspective

The feline purr, a sound that is simultaneously soothing and enigmatic, has been a subject of scientific curiosity for years. Traditionally, researchers believed that voluntary muscle contractions produced purring. However, a recent study sheds new light on this phenomenon, suggesting that this uniquely feline vibration may align more closely with the myoelastic aerodynamic theory of phonation.

Published in Current Biology, this research investigates the biomechanics of purring, a sound emitted by domestic cats when they feel comfortable or stressed. The study presents a perspective that relates the purring to a snore rather than a voluntary muscle spasm. The researchers argue that connective tissue masses embedded in the vocal folds of cats' larynges may enable felines to produce self-sustained low-frequency oscillations without neural input or muscular contractions.

What Is a Purr?

Until now, it has been widely believed that voluntary muscle contractions caused the vibratory component of purring. These contractions are initiated when the nervous system generates a signal which travels through a motor neuron to a neuromuscular junction. There, a chemical message is released, tensing the fibers and triggering a movement.

Contrary to this belief, the authors of the new study suggest that purring results from the laryngeal pads of cats. This view aligns with the myoelastic aerodynamic theory, which posits that vocal fold oscillation is produced due to asymmetric forcing functions over closing and opening portions of the glottal cycle. The research team argues that the flow of air entering and leaving the lungs activates the vibrations of the vocal cords, producing sounds similar to a human voice or characteristic animal sounds.

Why Do Cats Purr?

Cats purr throughout their lives, beginning as kittens. The reasons behind this phenomenon still need to be fully understood. However, general conclusions drawn by biologists, veterinarians, and animal scientists suggest that kittens purr to help their mothers locate them, purring encourages wound healing, and purring produces serotonin, which is why it is often compared to human smiles. Interestingly, domesticated cats do not only purr when they are content but also when they are stressed.

The findings of this new study have sparked some controversy. Biomechanical engineers interviewed by Science argue that the experiment could have been more extensive as it focused on the functioning of the larynx in isolation without considering the complex systems of a living cat, representing a significant oversight. Yet, the new research brings fresh insights and adds to our understanding of the mysterious feline purr.