[The reciprocal training of Drosophila individuals in a group situation by the trial-and-error method].

In the group situation, fruit flies try to avoid conflicts in which they kick each others. At first they attempt to escape from each other thus increasing run frequency as compared with control solitary individuals, but shortly terminate runs in order to prevent collisions. Motoric activity and conflict frequency during encounters are high in such situations. From the very beginning, probability of transition from activity to direct contact is higher than that from rest to contact or from preening to contact. Therefore, during the first 5 minutes a fly learns to increase interval between runs using the trial-and-error method. Besides abrupt decreasing of number of collisions and activity of flies in group as compared with control, operant training leads to formation of passive aggregations, because closely situated flies avoid to display activity. A new behavior reaction is developed, as well, namely immobile fly initiate preventive touches by legs. Such training is adaptive because in the natural aggregations of flies on fermented fruits it increases aggressive activity decreasing thus raising efficiency of feeding on a common substrate.