The key thesis of this work stipulates that current human-computer interfaces for education and rehabilitation can be greatly improved by recognizing the long-term need for a novel communication layer that can serve as an intermediary between users and today's systems of ever increasing complexity. A special education and rehabilitation system employs real-time interactive computer graphics and photorealistic virtual humans to implement an emotional modulation technique that increases learning efficiency. Emotions play a vital role in a student's ability to memorize and learn new material. Emotions act as a catalyst in the process of transforming information into knowledge, and thus the effectiveness of computer-based learning can be greatly improved if we incorporate emotions into computer use as a learning tool. Tutors, teachers, and professors achieve this effect - called emotional modulation-on a daily basis, using their charisma and other personal and motivational qualities during the time they invest in their students. Therefore, using virtual humans to mimic the natural face-to-face dialogue that normally takes place between student and tutor in real life forms the foundation of a unique and critically important enabling technology for teaching in the future.