Here are two clips of cats purring. One of the clips is from a cat who is happy and content, and the other is from a cat who is hungry and wants you to feed it.

Clip 1:

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Clip 2:

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Can you tell which is which?

The answer, given by what is surely the cutest ScienceNOW article ever posted, is that the first purr is from a happy cat, and the second purr is from a hungry cat.

The difference between the purrs is that the “solicitous” (or hungry) purr contains a high-frequency element that the “nonsolicitous” (i.e. happy) purr lacks, according to a paper published Tuesday in Current Biology by behavioral ecologist Karen McComb. The resulting sound is rated by participants in the study as more unpleasant and urgent-sounding. Presumably, this is one subtle way the cats get their owners to feed them.

Experts quoted in the article suggest that the different purrs are a sort of learned behavior, by which cats “train” their owners to take good care of them. This seems a bit fanciful, but is interestingly reminiscent of Michael Pollan’s whole way of looking at evolution from a non-human perspective.

PS: For the computer game nerds out there, does anyone else think the hungry cat sounds suspiciously like a zergling?