Suchergebnisse

Using a task which closely simulated the actual output from a sonar device, the performance of 12 subjects was observed for a total of 115 hr in repeated prolonged monitoring sessions under auditory, visual, and dual-mode display conditions. Despite an underlying basic superiority of signal discriminability on the visual display, and the occurrence of long-term practice effects, detection rate was consistently and substantially higher under the auditory condition, and higher again with the dual-mode display. These results are similar to those obtained by earlier workers using artificial laboratory tasks for shorter periods, and are consistent with the notion that auditory displays have greater attention-gaining capacity in a "vigilance" situation. A further comparison of the auditory and visual displays was then made in an "alerted" situation, where the possible occurrence of a signal was indicated by a warning stimulus in the alternative sensory mode. Ten subjects were observed for a total of 57 hr in these conditions, under which performance was found to be clearly superior with the visual display. Cross-modal correlations of performance indicated the presence of a common factor of signal detectability within subjects. It was concluded that where efficiency both in the initial detection of targets and their subsequent identification and tracking are equally important, the best solution would seem to be to retain both auditory and visual displays and to ensure that these are monitored concurrently.

Changes in performance at a visual vigilance task over eight 40-minute sessions were studied in three groups of eight subjects. The task was to inspect a series of displays of small disks for the occasional presence of a disk of slightly greater area than the others. For one group (search), each display consisted of a row of six disks. For one of the two no-search groups, the display contained two adjacent disks, one of which served as a reference standard; for the other group this reference disk was absent. Substantial improvement in overall detection rate occurred in all three groups. Analysis indicated that in each case this improvement was due to a genuine increase in discriminatory efficiency and not to any change in response criterion. Neither search nor the presence or absence of a reference standard appeared to affect the degree of improvement observed to any marked extent. Within-session decrement was observed only in the search group; this decrement was found to result from a change in response criterion, and not from any alteration either in discriminatory efficiency or search strategy.