Clutter and Display Conformality: Changes in Cognitive Capture

HUD technology has provided pilots with a variety of performance advantages over traditional head-down cockpit displays. Reduced visual switching times, increased situational awareness, and a variety of flight performance improvements have all been associated with HUDs. Despite these advantages, research has identified some possible HUD shortcomings. Objective and subjective data suggest HUDs increase the difficulty associated with switching one's attention among stimuli within the same visual space, causing pilots to inappropriately fixate on the display, a state termed cognitive capture. Possible factors that might affect cognitive capture include display conformality, clutter, and perceptual separation. The present research used reaction time data to assess the effects of these factors on cognitive capture. Sixty participants completed a simulated ship navigation task using either a conformal or non-conformal HUD. Each of four trials was factorial for display clutter (low, high) and obstacle probability (low, high). Reaction time data showed a performance advantage for conformal displays particularly in the high clutter condition. Subjective data revealed that the conformal display was less distracting, appeared to depict fewer instruments, and required less effort to attend to the environment than the non-conformal display. Findings concerning perceptual separation were inconclusive.