Abstract : Data are presented which suggests that degree of Hemispherica alpha asymmetry (for tasks hypothesized to induce such asymmetries) is related to resting eyes closed endogenous alpha activity. Also, it is demonstrated that frontal theta activity varies with difficulty level of an addition task. Both results share a common emphasis on electrophysiological individual differences. EEG recordings from 54 right-handed subjects (P3, P4, f3, f4 referenced to linked ears) performing 5 cognitive tasks were collected and quantified using period analysis. The subjects were rank ordered on the basis of their hemispherically averaged (P3+P4/2) alpha activity during an Eyes Closed (lights off) baseline condition. Subjects comprising the top, middle and lower thirds of this ranking were ascribed the status of HIGH, MIDDLE or LOW alpha generators. A similar procedure was performed for frontal theta to distinguish theta generators. Before the experiment the tasks were ordered a priori for their hypothesized hemispheric involvement. (js)