Psychophysiological measures can be used to determine whether a particular display produces a general difference in brain function. Such information might be valuable in efforts to improve usability in display design. In this preliminary study, we aimed to use the electroencephalography (EEG) task load index (TLI), given by the ratio of mean frontal midline theta energy to mean parietal alpha energy, to provide insight into the mental effort required by participants performing intuition-inducing and analysis-inducing tasks. We employed behavioral measures (reaction time and percent correct), and a subjective measure (NASA-Task Load Index) to validate the objective measure (TLI). The results we obtained were consistent with our hypothesis that mental effort required for analysis-inducing tasks would be different from that required for intuition-inducing tasks. Although our sample size was small, we were able to obtain a significant positive correlation between NASA-Task Load Index and TLI.