The general activation level (GAL) is one of the sources of influence in psychophysiological experiments. That means most of the results are dependent on the GAL. Taken this into account one can furthermore elucidate a part of the high variability of the interesting physiological data. We analysed heart rate (HR), auditory evoked potentials (AEP) elicited by background stimuli and the subjective assessment of the internal state of the subjects to describe changes of the GAL. Summarizing the results we can show different influences of the GAL on the physiological data. Changes of HR and AEP-parameters are caused by specific experimental conditions. The distinct influence of the subjective state of the subjects on the AEP-shapes allows the conclusion that subjective data should be more taken into consideration. The comprehensive characterization of the GAL requires data of different integrative levels.