1. A computer-aided-educational method for educating a student on a subject through a computer, which includes a presenter and a non-intrusive sensor, the method comprising the steps of: presenting study materials on the subject to the student through the presenter; monitoring automatically more than once the student's concentration-sensitive behavior through the sensor while the student is studying the materials; analyzing the monitored results based on one or more rules; and providing an indication on the student's concentration level based on the analysis.