The Effects of Goal-Landmark Distance on Overshadowing: A Replication in Humans (Homo sapiens) of Goodyear and Kamil (2004)

Goodyear and Kamil (2004) assessed the ability of Clark's nutcrackers to find buried food based on a cross-shaped array of landmarks at different distances from the goal. Their findings suggested that proximal landmarks overshadowed learning about distal landmarks, and this was attenuated when assessing the effect of distal landmarks on learning about proximal landmarks. In this study, we aimed to replicate their findings in human spatial navigation by using a virtual environment. Three groups of participants were trained in an open environment featuring orientation cues, and they had to find a hidden goal with reference to four landmarks that were arranged in the shape of a cross and placed at different distances from the goal. Two of the four landmark distances were common across all three groups to allow a comparison of the extent of overshadowing under comparable conditions. Following training, all participants were tested with each of the four landmarks individually. Consistent with the results in birds, we observed better performance in the groups with more distal landmarks, suggesting that overshadowing was greater in the groups with closer landmarks and thus dependent on the spatial distance between the landmarks and the goal. Landmarks near the goal more effectively overshadowed landmarks far from the goal. A second experiment, in which landmarks and orientation cues were misaligned in order to prevent the use of a straightforward solution to the task, replicated the results. The results are discussed in terms of a modification of Pearce's configural model.