Foraging desert ants return to their nest by following landmarks that may be remote from the nest. Landmarks are objects with a distinctive visual pattern. Ants are able to compare the real time visual information from a landmark with a snapshot memory of the landmark that is retrieved from the brain. The ant “recognizes” its position when reality aligns with memory. For ants approaching a landmark that they must navigate around, the ants associate “turn right” or “turn left” around the landmark. How do ants learn which direction to turn?
In navigating around an object for the first time, an ant will randomly choose “turn right” or “turn left”. A decision that minimizes the return path will be reinforced during subsequent trips and the ant will always associate a turn in that direction with the landmark. If a turn increases the return path to the nest, then that turn will not be reinforced and the ant may choose to turn in the opposite direction around the object in subsequent trips. After the initial trial and error, the ant will associate the direction of turn that creates the shortest path. In this way, the ant learns its way home by associated both landmarks and turn direction to follow a path home.
T.S. Collett*, E. Dillmann, A. Giger, and R. Wehner. 1992. Visual landmarks and route following in desert ants. J Comp Physiol A 170:435-442.