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Velma L. Velazquez

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Publications by Velma L. Velazquez (bibliography)

1992

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Velazquez, Velma L. and Tsang, Pamela S. (1992): Is Performance Tradeoff an Experimental Artifact?. In: Proceedings of the Human Factors Society 36th Annual Meeting 1992. pp. 1403-1407.

“The purpose of the present study was to examine the utility of the resource notion, which is the basis for the secondary task technique of workload assessment. The unbiased optimum-maximum method proposed by Navon (1984) was used to manipulate task priority without conveying to the subjects that time-shared performance must tradeoff. Three task pairs that fell on a continuum of degree of shared resources were tested. The data showed that performance tradeoff is not an experimental artifact. Moreover, the data suggested that increased degree of shared resources led to increased resource allocation optimality and decreased time-sharing efficiency, as predicted by multiple resource theories. The present data suggests that resource theories are useful in explaining dual task performance, and that the secondary task can be a useful workload assessment tool.”

1991

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Tsang, Pamela S. and Velazquez, Velma L. (1991): Utility of Secondary Task as a Workload Assessment Technique. In: Proceedings of the Human Factors Society 35th Annual Meeting 1991. pp. 1481-1485.

“Recently Navon (1984) suggests that much of the dual task data that lend support to resource theories are methodologically flawed and that there are non-resource related mechanisms such as outcome conflict that could explain dual task data equally well. If Navon's concerns can be validated, the current view of workload as a resource-related concept would have to be revamped. The present research examined performance tradeoff -- demonstration of resource allocation -- with the optimum-maximum method. The optimum-maximum method was a variation of the secondary task technique proposed by Navon to encourage maximum joint task performance without conveying to the subjects that task performances must tradeoff. A continuous tracking task and a Sternberg memory task were used; three priority levels were used to induce resource allocation. An absence of performance tradeoff with the optimum-maximum method would support Navon's claim that performance tradeoffs may not be true indications of resource competition or task demand and therefore not reliable reflection of mental workload. Performance tradeoff was observed when the tracking task was optimized. When the Sternberg task performance was optimized, Sternberg performance was sensitive to the priority manipulations but the concurrent tracking performance was not. Peripheral vision was proposed to have protected the tracking performance when subjects were visually focusing on the Sternberg stimuli. However, the peripheral vision hypothesis could not account for the graded performance changes across priority levels. The present data suggest that the resource view is still a useful concept and the secondary task technique still could provide informative disclosure about task demand and mental workload.”

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