What's in a growl?

Can you tell a dog's size by its growl? A recent study by the University of Sussex found that most of their human testers could reliably guess a dog's size just by listening to a recording of growls.

Anna Taylor, a psychologist at the University, and her team recorded growls from 30 domestic dogs of 22 different breeds. A researcher would go to the dog's residence with recording equipment, approach the dog and stare into its eyes. The dogs took this as an intimidating move and would growl.

Researchers played these growls back to over 50 human volunteers, who were asked about the size of the dog. At one point, the listeners also heard growls that had been altered to reflect sounds you might expect to hear from larger or smaller dogs.

In almost all cases, the listeners correctly guessed the general size of the dog just by its growl, even though the sizes ranged from a 77-pound Rottweiler to a 2.2-pound miniature Dachshund. The researchers were able to predict how the listeners would rate the artificially manipulated growls.

One possible finding is that humans are able to acoustically detect a dog's size because dogs and humans have evolved so closely.