| Summary: | Rating scale techniques have been recommended for mental workload assessment. The Modified Cooper-Harper (MCH) Scale is a decision tree scale which has proven to be a reliable indicator of workload. Five additional rating scales were developed to examine rating scale features including a) number of rating scale alternatives, b) decision tree format, c) decision tree hierarchy, and d) (two) computer-implementation(s). The purpose of this study was to improve the sensitivity of the MCH Scale and to try to identify what aspects of the scale contribute to its effectiveness.
A simulated flight task emphasizing mediational (cognitive) behavior was used to present low, medium, and high levels of loading to 6 student and thirty licensed pilots. In a Singer-Link GAT-1B flight simulator, the pilots performed three counterbalanced load level flights. After each simulated flight, a rating scale and questionnaire was administered.
The results indicated that the paper rating scale having 15 response alternatives and the original decision tree was the most sensitive to load. Both 10-point modifications, the computerized version of the MCH Scale and the version with the decision tree format removed, were somewhat superior to the original MCH Scale, which was also sensitive to load. These findings, however, are not consistent with those obtained in a companion study of communications tasks, indicating that these rating scale measures are task dependent. Use of the MCH Scale is recommended since it alone has consistently demonstrated sensitivity to load across tasks and across studies. === M.S.
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