North is up(hill): route planning heuristics in real-world environments.

Navigators use both external cues and internal heuristics to help them plan efficient routes through environments. In six experiments, we discover and seek the origin of a novel heuristic that causes participants to preferentially choose southern rather than northern routes during map-based route planning. Experiment 1 demonstrates that participants who are tasked to choose between two equal-length routes, one going generally north and one south, show reliable decision preferences toward the southern option. Experiment 2 demonstrates that participants produce a southern preference only when instructed to adopt egocentric rather than allocentric perspectives during route planning. In Experiments 3-5, we examined participants' judgments of route characteristics and found that judgments of route length and preferences for upper relative to lower path options do not contribute to the southern route preference. Rather, the southern route preference appears to be a result of misperceptions of increased elevation to the north (i.e., north is up). Experiment 6 further supports this finding by demonstrating that participants provide greater time estimates for north- than for equivalent south-going routes when planning travel between U.S. cities. Results are discussed with regard to predicting wayfinding behavior, the mental simulation of action, and theories of spatial cognition and navigation.