Attentional Issues with Superimposed Symbology: Formats for Scene-Linked Displays

Foyle, David C.; McCann, Robert S.; Shelden, Stephen G. · 1995 · ROSA P / United States. National Aeronautics and Space Administration. Operations Branch

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Summary

This study investigates "attentional tunneling," a phenomenon where pilots using Head-Up Displays (HUDs) fail to simultaneously process superimposed symbology and the out-the-window visual scene. Previous research indicated that while HUDs improve specific tasks like altitude maintenance, they can degrade performance in other areas, such as detecting runway incursions or following ground paths, due to the differential motion between fixed-screen symbols and the moving world. The authors hypothesized that this performance tradeoff is caused by differential motion rather than the cognitive load of digital formats. To test this, they proposed "scene-linked" symbology, where virtual symbols move with the environment, eliminating differential motion cues. The experiment employed a within-subject design with 14 participants using a flight simulator. Subjects were tasked with maintaining a 100-foot altitude and following a meandering ground path marked by pyramids under turbulent conditions. Five HUD symbology conditions were tested: superimposed digital, superimposed analog, scene-linked digital, scene-linked analog, and a control condition with no altitude display. Performance was measured using Root Mean Square Error (RMSE) for both altitude and lateral path deviation. The study aimed to determine if scene-linked symbology would eliminate the performance tradeoff observed in superimposed conditions and whether the format (digital vs. analog) influenced attentional tunneling. Results confirmed that superimposed symbology (both digital and analog) replicated the attentional tunneling effect: altitude maintenance improved significantly compared to the control condition, but path maintenance performance worsened. This indicated that the performance tradeoff was independent of the display format, ruling out processing load as the primary cause. In contrast, scene-linked symbology (both digital and analog) eliminated the tradeoff. Not only did scene-linked displays improve altitude maintenance, but they also significantly improved path maintenance performance compared to the control condition. This suggests that removing differential motion allows for efficient parallel processing of symbology and the external scene. The findings conclude that attentional tunneling in HUDs is driven by differential motion between the symbology and the visual scene. Scene-linked symbology offers a viable design solution to mitigate this issue, enhancing overall situational awareness. The authors discuss applications for low-visibility surface operations, proposing scene-linked virtual instruments and scene augmentations (such as virtual taxiway markers and turn warnings) to aid pilots during taxiing. These displays, which require accurate positioning systems like Differential GPS, could reduce spatial disorientation and improve safety by allowing pilots to process navigation data and environmental cues simultaneously without attentional switching penalties.

Key finding

Scene-linked symbology improved both altitude and flight path maintenance without the performance tradeoff observed with superimposed symbology.

Methodology

simulator

Sample size: 14

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

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• hud ar windshield