Natalie L. Anderson, Adam Barnas, Ryan N. Fuentes, Kevin Longacre, Natalya N. Lynn, Katherine Y. Peters, Nicole A. Schlater, Jeremy T. Schwob, Adam D. Sitz



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The Muller-Lyer illusion is a well-known geometric illusion in which pairs of lines of the same length are perceived to be different because of forms (e.g. "finsÂ") at the ends of the lines. This influence of context upon the perception of line length is well-established for 2-D illusions but has also been demonstrated in larger-scale, three-dimensional spatial tasks (Wraga, Creem and Proffitt, 2000). Across three experiments, we utilized a large-scale, walkable variation of the Muller-Lyer illusion to examine the effect of context upon the perception of egocentric distances. Whereas the traditional Muller-Lyer illusion utilizes geometric forms at the end of lines to manipulate the context of the line, we employed human forms to manipulate context. In each experiment, participants viewed a human target facing either towards or away from them and were then asked to judge the distance to the target. We predicted that the facing direction of the human target would influence magnitude estimates of target distance, similar to the way geometric forms at the ends of lines influence judgments of line length. However, we also predicted that action-based indicators of perceived distance (e.g. walking to the previously-viewed target person with eyes closed) would not be influenced by the contextual information provided by the human target's facing direction. In Experiments 1 and 2, participants viewed human targets that were facing toward or away and then, with eyes closed, walked a distance that matched the perceived distance to the target person. Results from these experiments suggest that action-based indicators of perceived distance are immune to contextual influences of human target facing direction. In Experiment 3, participants will view human targets that are either facing toward or away, but will verbally estimate the distance to the target. Together, these results will speak to the role of contextual information in spatial perception.

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Project Designation

Independent Research

Primary Advisor

Benjamin R. Kunz

Primary Advisor's Department



Stander Symposium poster

The Effect of Context Upon the Perception of Egocentric Distance Using a Walkable Human Muller-Lyer Illusion