A comparison of methods of assessing cue combination during navigation.

Mobile organisms make use of spatial cues to navigate effectively in the world, such as visual and self-motion cues. Over the past decade, researchers have investigated how human navigators combine spatial cues, and whether cue combination is optimal according to statistical principles, by varying the number of cues available in homing tasks. The methodological approaches employed by researchers have varied, however. One important methodological difference exists in the number of cues available to the navigator during the outbound path for single-cue trials. In some studies, navigators have access to all spatial cues on the outbound path and all but one cue is eliminated prior to execution of the return path in the single-cue conditions; in other studies, navigators only have access to one spatial cue on the outbound and return paths in the single-cue conditions. If navigators can integrate cues along the outbound path, single-cue estimates may be contaminated by the undesired cue, which will in turn affect the predictions of models of optimal cue integration. In the current experiment, we manipulated the number of cues available during the outbound path for single-cue trials, while keeping dual-cue trials constant. This variable did not affect performance in the homing task; in particular, homing performance was better in dual-cue conditions than in single-cue conditions and was statistically optimal. Both methodological approaches to measuring spatial cue integration during navigation are appropriate.