The Influence of Set Size in a Dynamic Decision-Making Task

Patton, Colleen E.; Wickens, Christopher D.; Clegg, Ben; Smith, C. A. P. · 2024 · AHFE international

DOI: 10.54941/ahfe1004877

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Summary

This study investigates the impact of set size on dynamic decision-making in maritime contexts, specifically focusing on the identification of hostile entities based on movement patterns. While multiple object tracking (MOT) literature establishes that increasing the number of distractors reduces accuracy, real-world scenarios often require operators to accumulate evidence over time to determine intent. The authors aimed to determine if increasing the number of vessels to monitor exacerbates the difficulty of identifying hostile behavior, such as "hunting" (closing distance) or "shadowing" (maintaining constant distance), in a dynamic environment. The experiment utilized a simulation where 35 participants controlled their own ship while monitoring three, six, or nine computer-controlled vessels. One vessel exhibited hostile behavior, while others acted as distractors with random or patrol movements. Participants moved their ship up to 35 times to gather evidence before identifying the hostile ship and its behavior. The design manipulated set size (3, 6, or 9 ships) and measured accuracy, the number of steps taken (evidence accumulation), and the influence of initial distance between ships. Results indicated that overall accuracy was low, averaging 53%, with hunting ships identified more accurately (59%) than shadowing ships (47%). Contrary to standard MOT findings, accuracy above chance did not significantly differ across set sizes. However, participants took significantly more steps as the number of ships increased (averaging 15.3 steps for three ships, 17.5 for six, and 19.8 for nine), though all averages remained well below the maximum of 35 steps. Accuracy was strongly correlated with the number of steps taken. Additionally, distance negatively impacted accuracy, particularly for hunting behaviors, replicating previous findings. The authors conclude that working memory limitations likely cap performance at low levels regardless of set size, preventing the typical decline in accuracy seen in static MOT tasks. Participants appeared insufficiently calibrated to the increased workload, taking only marginally more steps despite higher distractor counts. These findings suggest that human operators struggle with the cognitive demands of accumulating evidence in crowded environments. The study highlights the need for automated aids, such as history trails or decluttered displays, to support working memory and improve decision-making speed and accuracy in safety-critical naval operations.

Key finding

In a dynamic decision-making task, increasing the number of tracked objects did not significantly reduce accuracy above chance, but participants took more steps to gather evidence as set size increased.

Methodology

simulator

Sample size: 35

Provenance

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