ABSTRACT: This is a case study involving empirical assessments of EEG signals collected using a Neuro Scan Electrical Signal Imaging brain recording system with 256 electrodes (ESI-256). Subjects were used in an effort to determine and contrast the mental efforts associated with given tasks involving different human-computer interfaces. This article demonstrates and confirms that indeed a particular frequency band between 8 and 13 Hz referred to as alpha activity can be used to charcterize under different events or conditions the mental effort or activation associated with basic sensory experiences and mental tasks. The results obtained in this study support this assertion.