Egocentric and allocentric search: effects of platform distance and environmental cues.

Three water maze experiments with rats examined egocentric vs. allocentric search as a function of platform distance and the predictiveness of the start trajectory and environmental cues. In Experiment 1, rats trained to a Near platform predicted both by landmarks and a fixed start trajectory showed approximately equal egocentric and allocentric search when tested from a novel start location. Rats trained to a Far platform and tested the same way predominantly showed allocentric search. In Experiment 2, rats trained to a Near platform predicted only by landmarks or background cues showed predominant egocentric search. In Experiment 3, rats trained to a Near or a Far platform with a fixed trajectory and no landmarks, showed predominant egocentric. Non-predictive landmarks reduced egocentric search in rats trained with a Far, but not with a Near platform. Overall, with increased goal distance, rats decrease dependence on an egocentric trajectory and increase attention to surrounding landmarks. These results add to the developing notion that animals use both egocentric and allocentric search balanced by environmental conditions, such as distance to the goal and the number of landmarks.