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Theodore E. Cohn, Khoi Nguyen; Turning it on piecemeal makes it seen faster. Journal of Vision 2002;2(7):232. doi: https://doi.org/10.1167/2.7.232.
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In real-world signaling situations, rapid detection of a signal can be vitally important. One such situation involves a following vehicle (FV) that is too close to a lead vehicle (LV). Suppose that the LV could detect the problem. How should the FV be signaled? We studied visual warning signals typical of those used on large LV's, like buses: in this case, an eight-segment 8 CM × 150 CM horizontal array.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
The endpoint measure was time to react to light onset in the array (RT). The ‘standard’ signal involved simultaneous ignition of all eight segments at t=0. The ‘test’ signal delayed the ignition of some segments (first 4,5 @ t=0; then 3,6; then 2,7; then 1,8, each step in the sequence delayed by 50MSEC) producing an apparently expanding pattern. Observers included 6 pre-presbyopic, normal, corrected adults plus 3 corrected adults over 60. Conditions that were varied during testing included adaptation level, array intensity and array size (19 DEG or 1.9 DEG). 25 repetitions of each signal were tested for each condition. Paradoxically, faster RT's occurred with piecemeal ignition. Median RT's were sometimes faster by as much as 50 MSEC and once, by 100 MSEC for individuals, compared to RT's for simultaneous ignition. The difference was due mainly to increased numbers of late RT's for the ‘standard’. In nearly every condition, the ‘test’ signal was seen significantly more quickly than the simultaneous signal. The exception involved a ‘wig-wag’ signal in which we turned on 1,2,5, &6 then, later, 3,4,7,&8.
The paradox can be explained if one presumes that the standard signal does not stimulate M-neurons (or, some might suggest, ‘looming’ detectors) as well as does the piecewise-delayed ‘test’ signal. To determine whether a real-world LV-FV situation can benefit from this knowledge, a delayed test-signal will soon be deployed on a transit bus LV equipped with a radar-based FV detector.
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