  In this paper, I present the evaluation of a novel knowledge domain
visualization of educational technology. The interactive visualization is based
on readership patterns in the online reference management system Mendeley. It
comprises of 13 topic areas, spanning psychological, pedagogical, and
methodological foundations, learning methods and technologies, and social and
technological developments. The visualization was evaluated with (1) a
qualitative comparison to knowledge domain visualizations based on citations,
and (2) expert interviews. The results show that the co-readership
visualization is a recent representation of pedagogical and psychological
research in educational technology. Furthermore, the co-readership analysis
covers more areas than comparable visualizations based on co-citation patterns.
Areas related to computer science, however, are missing from the co-readership
visualization and more research is needed to explore the interpretations of
size and placement of research areas on the map.
