New York ? A cat’s purr normally says, “I’m happy.” But a new study suggests some purrs send cat owners a much different message: “Feed me!”

Researchers found that purrs of hungry cats included a higher-pitched sound, somewhat like a cry or meow. They played recordings of these purrs from 10 cats to 50 human volunteers.

Even people who’d never owned a cat found them to be more urgent and less pleasant than contented purrs from the same animals.

These food-seeking purrs may exploit the way humans naturally respond to a baby’s cry, the researchers suggest.

Not all cats use this strategy, but some apparently learn to turn it on when they see it’s effective in getting a human to feed them, Karen McComb of the University of Sussex in England said in a statement.

She and co-authors present their work in today’s issue of the journal Current Biology.