The empirical research described in this book comprised three experimental phases. In the first phase, an initial experiment was carried out to explore and compare the usability and learning performance of facially animated expressive avatars with earcons and speech, and text with graphics metaphors. The second experimental phase involved an experiment conducted to investigate users perception of avatar s facial expressions and body gestures when presented in both the absence and presence of interactive e-learning context. In addition, the experiment aimed at evaluating the role that an avatar could play as virtual lecturer in e-learning interfaces by comparing the usability and learning performance of three different modes of interaction. The third phase experimentally examined a novel approach for the use of earcons and auditory icons in e-learning interfaces to support an animated facially expressive avatar with body gestures during the presentation of the learning material. The obtained results demonstrated the usefulness of the tested metaphors to enhance e-learning usability and to enable users to attain better learning performance.