A study published in the Journal of the Acoustical Society of America presents the world's first evidence that size can be assessed on the basis of vocal signals. Anna Taylor, a psychologist at the University of Sussex, and her colleagues recorded growls emitted by 30 privately owned domestic dogs of 22 different breeds. An experimenter would get a dog to growl by showing up at the dog's house, approaching it and then staring into its eyes. The dog perceives this as an intimidating move and emits a defensive growl. The researchers then played these growls back to over 50 human listeners, who were asked, "What is the size of this dog?" In virtually all cases, the listeners correctly guessed the general size of the dog, be it a 45 kilos Rottweiler or a miniature Dachshund, based on just the animal's growl.