Experimental studies of the ability of ants to add and subtract small numbers.

Ants had to communicate information to each other in an apparatus consisting of a horizontal "trunk" with "branches" in order to obtain food, the information being used to identify which of 40 branches had a feeder. The feeder was placed on two preselected branches significantly more frequently than on the other branches. The ants were able to tune their communication system such that the duration of communications was related to the frequency with which feeders were located on branches, and the ants could add and subtract small numbers during communication of information on the feeder identification number.