Preliminary Support for the Line Bias Illusion as a Contributor to Black Hole Effects

ABSTRACT Objective We tested the plausibility of the hypothesized Line Bias Illusion to explain a spatial disorientation phenomenon known as the Black Hole Illusion (BHI): in the absence of a visible horizon, pilots misjudge an implicit horizon from the convergence point of parallel runway edge lines. Background BHI occurs when impoverished visual conditions at night cause pilots to fly too low on landing approaches. Multiple hypotheses have been proposed to explain BHI, without clear consensus in the literature. Method We conducted multiple experiments in which participants judged the intersection point of dotted lines on a computer screen. In Experiment 1, participants placed a horizon line where they believed two converging dotted line segments should intersect. In Experiments 2A and 2B, participants estimated the intersection point of single dotted line segments with a separate solid line. Results Participants in Experiment 1 tended to place the intersection point of two converging lines too low on the computer screen. Participants in Experiments 2A and 2B tended to respond as if the stimulus lines were more horizontal than actually presented. Conclusion Our findings are consistent with the hypothesis that pilots misjudge the location of an implicit horizon based on the runway edge lines. In the context of a visual spatial strategy that assumes a stable horizon, such a misperception may cause pilots to adopt a low flight path.