Abstract
The criterion validity of the NASA Task Load indeX (TLX) and a previously developed subjective Task Complexity Index (TCI) were studied. A measure of subjective task complexity was hypothesized to complement the NASA TLX subjective workload measure on prediction of performance on complex problem-solving tasks. Twelve licensed nuclear power plant operators participated in a study with 16 simulated realistic scenarios. Although the study indicated some validity for both the TLX and the TCI, the results indicated stronger criterion validity for the subjective task complexity measure than for the TLX. Factor analysis of the task complexity ratings and TLX ratings together indicated that the 2 measures represent different constructs. Implications of the research include the recommendation of assessing subjective task complexity when studying human-machine configurations dealing with complex problem-solving tasks.