Interesting topic and research.
But, I couldn`t find any description of the how the recording of the lecture that the students watched was done. I`m thinking mostly on how the quality of audio and video was. From my own experience audio quality is most important! OK level, no hiss, quality of audio (not much room echo and good mic) are something everyone can hear. I would argue that even the non-audio-interested-person can hear this, they just don`t realise it.
What are your thoughts?