The experimental literature on the dfects of color on visual search and identification performance was reviewed. Forty-two studies published between 1952 and 1973 were located that gave results which could be used to determine the effectiveness ofcolor codes relative to various types ofachromatic codes. Quantitative analyses of these results indicated that color may bea very effective performance factor under some conditions, but that it can be detrimental under others. Tentative conclusions about the nature of these conditions were derived from the results. A guide for design decisions and an indication of knowledge gaps are also provided.

Four subjective workload scales were compared along four dimensions: sensitivity, operator acceptance, resource requirements, and special procedures. The scales were the Modified Cooper-Harper scale, the National Aeronautics and Space Administration Task Load Index (TLX), the Overall Workload (OW) scale, and the Subjective Workload Assessment Technique. Three U.S. Army systems were studied for potential workload concerns. Data from five different studies on the three systems were compared along the aforementioned four dimensions. Results indicate that all four scales are acceptable tools and are sensitive to different levels of workload. However, TLX and OW are consistently superior when considering sensitivity, as measured by factor validity, and operator acceptance. This research is an example of a systematic approach for examining human factors measurement tools.

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Four empirical operator workload (OWL) scales were applied to ground control operations of the Aquila RPV during a recent field test: NASA TLX, SWAT, Overall Workload (OW), and the Modified Cooper-Harper (MCH). Seventeen sets of individual assessments of mission segments were made by the four members of each of four crews and one replacement crewman. Jackknife factor analysis revealed the presence of only a single factor and indicated that the mean factor loadings formed a consistent ordering ( F(3,48) = 503.5, p < .00005): TLX (.910) > SWAT (.893) > OW (.869) > MCH (.833). ANOVAs also examined the effects of various variables on the composite workload factor scores; significant findings were found which reflected both upon the system and its test. These findings as well as informal lessons learned are discussed in the context of the development and validation of a methodology for assessing OWL.

A series of nine experiments are reported in which highly practiced subjects were used to investigate the use of letters, digits, familiar geometric shapes, and colored dots as coding dimensions in visual displays. These experiments used single-code and dual-code displays in three isolated tasks (choice reaction, search and locate, and identification-memory) and in a multiple task that combined the three tasks in an irregularly alternating sequence. The results of these experiments provided no basis for concluding that any particular code has a general advantage or disadvantage over any other. Furthermore, when there were differences in performance with different codes, there was a tendency for practice to attenuate those differences. It is concluded that the relative effectiveness of different visual codes varies as a function of practice, other display conditions, the tasks, and the dependent measure used to make the comparison.