According to zoosemiotics animal communication involves an exchange of information between a sender and a receiver through a transfer of chemical signs. Described as representation and signification, a chemical sign can be produced without the presence of a dog and detected without the presence of the individual who produced it. This means dogs have the ability to leave their own signs and detect previously laid signs without the presence of another dog or individual. It is this theory of zoosemitoics that explains how dogs are able to determine the direction of a seemingly invisible scent track.