Viability of resource theories in explaining time-sharing performance.
The primary objective of the present research was to test for performance tradeoff induced by priority instructions with the purportedly unbiased optimum-maximum method. In experiment 1, performance tradeoff was observed when the tracking task was optimized but not when the Sternberg memory task was optimized. It was hypothesized that the tracking task was protected by peripheral vision when subjects focused on the optimized memory task. The second experiment tested the generality of the results with additional variations of the task pairs selected to represent different degrees of shared resources. The extent of performance tradeoff and time-sharing efficiency varied systematically with the extent of predicted resource overlap between the time-shared tasks. The observed performance tradeoff was strongly indicative of subjects' voluntary allocation control. Further, subjective ratings suggested that such control was effortful. These results were supportive of multiple resource theories and the viability of resource explanation of task interference.