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Seventeen subjects searched for, and then monitored, 3, 6, or 9 stationary targets in order to detect and shoot 3 threats. The targets were located in an area 1200 left and right and 900 upward, from straight ahead. They were viewed on a helmet-mounted display (HMD) by making appropriate head movements. The HMD had five different sizes of field-of view (FOV), ranging in width from 200 to 1 200. Subjects hit fewer threats and were threatened for longer durations with small FOVs than with large FOVs. The decrement in performance was dependent on the number of targets. Optimum performance with 3, 6, and 9 targets required FOVs of 200, greater than 200, and greater than 600, respectively. Subjects moved their head less, but faster, with large FOVs than with small FOVs. Also, there was an apparent inverse relation between head velocity while performing the task and error at replacing the targets afterward. It was interpreted that head velocity was mediated by the certainty with which subjects remembered target locations. It appeared that performance at the task was limited by how well subjects integrated information about target locations and not by how fast or how much they could move their heads.
Maxwell J. Wells (Mon,) studied this question.