Fig. 1. `Goal expansion' and `error compensation' strategies. Feeders (F) were surrounded by target circles painted on the desert floor, as shown for three nest-feeder distances D. The target circles were used for recording the ants' downwind approach distances d. The ants' approach towards the feeder may be governed by two alternate strategies: expectation according to the `error compensation strategy' (solid line) and expectations according to the `goal expansion strategy' (dashed lines; for details see text). Downwind angle is indicated for comparison with d; at 20 m nest-feeder distance, a schematic distribution of approach distances is illustrated, typical of, although narrower than, those recorded in the present experiments (compare Fig. 4).