Spatial Proximity Determines Overshadowing Between Landmarks in Human Spatial Navigation

Previous studies involving birds and humans have identified spatial proximity as a source of overshadowing between landmarks in navigation. In Herrera et al. (2024), subjects were trained in an open environment to find a hidden goal with reference to a cross-shaped array of four landmarks placed at various distances from it. Critically, two of the four landmarks (i.e., target landmarks) were placed at distances that were common among groups whereas the remaining two were either proximal or distal from them. Landmarks near to the goal overshadowed (i.e., competed with) learning about the further ones, and this effect disappeared in the groups trained with distal landmarks. However, neither of these studies included a control group providing a base line performance to assess the extent of competition; were the data indicative of overshadowing or facilitation of learning? Thus, we assessed whether spatial proximity determines overshadowing or facilitation between landmarks, including a control group trained with the target landmarks only. We conducted three experiments with varied training length: 6 training trials in Experiment 1 and 16 in Experiments 2 and 3. We also extended the distance of the landmarks to the goal in Experiment 3. In all experiments, we observed overshadowing in the groups trained with closer nontarget landmarks (relative to the target) but no overshadowing when the nontarget landmarks were distal from the target landmarks. Overall, these experiments reveal spatial distance is a critical determinant of overshadowing between landmarks, a finding that is consistent with domain-general theories of learning, such as a modification of Pearce’s configural model.