A study reveals the origin of cats’ purring

Cats’ purring is a sign that they are happy, content and feel settled, enjoying lots of fuss and attention. We all know that cats express their feelings by purring, in the same way that when humans are happy they smile and dogs wag their tails.

For the scientific community, the real mystery is how cats produce these purrs. Well, a recent study published in Current Biology seems to have found the answer: it is more similar to snoring than to a voluntary muscle spasm.

The most accepted hypothesis so far

To date, the most accepted hypothesis about the origin of purring was that of muscle construction. According to this idea, purring is produced by the vibration of the muscles of the larynx by contracting and relaxing rapidly and repetitively, about 30 times per second.

Muscle contractions make the vocal cords vibrate, generating the characteristic purring sound. However, this position is based on anatomical and physiological observations of cats, but there is no direct evidence to support it.

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Study procedure

Given these circumstances, a team of researchers from the University of Vienna led by Austrian scientist Christian T. Herbst has questioned the hypothesis of muscle contraction in feline purring, proposing an alternative based on the myoelastic-aerodynamic theory.

This theory focuses on how sounds are generated by the flow of air through elastic structures in the larynx, without relying on muscle contractions. To carry out the study, the researchers used the larynxes extracted from eight domestic cats euthanized after terminal illnesses, and with full knowledge and acceptance by their owners.

Next, they compressed the vocal cords of the larynx and blew warm, moist air through them. By doing this, they ensured that any sounds generated did not come from muscle contraction or brain intervention.

The discovery has sparked some controversy among experts.

T. Herbst and his colleagues were able to observe that purring occurred in all the removed larynxes, with self-sustained oscillations at low frequencies between 25 and 30 hertz. The explanation lies in a special 'pad' embedded in the vocal cords of cats, and observable with the naked eye.

This tool, without a doubt, would be an anatomical adaptation that reacts to the entry of air. According to this new discovery, purring would be a passive sound that would not require any muscular effort on the part of the cat.

Now, the scientific community is not entirely convinced. That is why the research team wanted to emphasize that their study does not seek to discredit the muscle contraction hypothesis, but rather to open a new avenue of research and highlight the need to review and delve deeper into which until now was considered the only valid explanation for feline purring.