Ants exhibit myriad complex social behaviors despite possessing only teeny brains. Now new research suggests that teaching should be added to the list of ant accomplishments.

Nigel Franks and Tom Richardson of the University of Bristol in England studied so-called tandem running in Temnothorax albipennis ants, during which two ants run a course between nest and food with various stops and starts en route. The researchers found that the lead ant who knows the way to the food slows down as the follower familiarizes itself with the route and will not proceed until the follower taps it on the back. The two also maintain a variable but matching speed and distance over time.

"This behavior is beautifully simple," Richardson says. "If one experimentally removes the follower and taps the leader with a hair at a rate of two times per second or more, the leader will continue."

Biologists have a definition of a teacher in the world of animals: any individual who sacrifices some potential gain in order to educate a nave counterpart. In a report published today in Nature Franks and Richardson argue that true teaching also requires feedback between teacher and student. The ant duos qualify on both counts. "The teacher provides information or guidance to the pupil at a rate suited to the pupil's abilities and the pupil signals to the teacher when parts of the 'lesson' have been assimilated and that the lesson may continue," Franks notes. "True teaching always involves feedback in both directions."

In the case of the ants, the teachers sacrificed their own speed, as evidenced by the observation that they reached the food source four times more quickly on their own than when they had a student in tow. But the students found food more than a minute faster with the help of their lesson and then often themselves became teachers for other ants. Sometimes, however, knowledge of a food source needs to be communicated faster than one-on-one training can accomplish. In those situations, large ant groups often broadcast such information through pheromone trails or other means. But tandem running proves that teaching may develop even in organisms that lack large brains, providing help for pupils with the tiniest of intellects.