Human performance can degrade as a result of an increasing cognitive workload. Especially in domains in which good task performance is crucial these effects are unwanted, and hence, need to be avoided. In Psychological literature studies have been presented which relate a variety of measures to the workload experienced by humans. However, these experiments have not been conducted with more complex tasks. In this paper, the aim is to perform a variety of measures to see whether combinations thereof can be used to predict performance of humans under tasks with varying complexity. A dedicated experiment has been conducted with 31 subjects, of which the results have been analyzed from both a statistical as well as a temporal perspective.