Researchers from the Max Planck Institute for Evolutionary Anthropology in Germany tested using the direction of their voice to indicate the presence of food to dogs.
In the first study, the experimenter stood behind an opaque wooden barrier and placed food in one of two containers in front of the barrier. Twenty-four adult dogs of various breeds participted in the experiment. After hiding the food, the experimenter crouched behind the barrier, out of sight of the canine research subject, and turned his or her face toward the treat-filled container, saying, "Oh, look, look there, this is great!" In an average of 7.6 out of 12 tries, the dogs correctly went to the food-containing box. Researchers eliminated other possible cues and determined that the dogs could not accurately guess where the food was if the speaker directed their voice to the back of the room.
In the second study, researchers recruited 16 puppies, ages eight to 14 weeks, and subjected them to the same test. The puppies were slightly better at following the direction of a person's voice than the adult dogs, finding the food an average of 8.1 out of every 12 tries. The puppies often took a few tries to catch on, however, and the puppies that had experienced more socialization with humans did better than those with limited human interactions.
In conclusion, researchers believe that the skill of finding food via human voice is learned, though very quickly and through a minimal amount of human exposure.
Source: Max Planck Institute for Evolutionary Anthropology via Live Science, 2014. New Trick: Pups Can Follow Human Voices to Food. Live Science online, May 2014.