Co-author Claudia Fugazza of Eötvös Loránd University in Budapest, Hungary, likens this ability to a person calling a hammer and a rock by the same name, or a child understanding that "cup" can describe a mug, a glass, or a tumbler, because they serve the same function. "The rock and the hammer look physically different, but they can be used for the same function," she said. "So now it turns out that these dogs can do the same."