According to studies done at the Mindlab 3d video is more "engaging" than 2d. I found this study interesting because it could be applied to a comparison of high-def music verses standard def or even MP3. But since someone would have to pay for the study, just as the Blu-Ray Disc Organization paid for this video study, chances of such a study being done are pretty slim.
So what was measured in the study? Mindlab used sensors to monitor EEG and EDA responses to stimulae. In the case of this study the stimulate consisted of 2 and 3D film clips.
Could the changes be attributed to anything besides short attention spans? Perhaps the added processing load on the human brain is the source of these changes and that alone accounted for the differences in brain activity.
As I mentioned earlier, I'd love to see this test done music-only on a darkened room comparing various resolutions of music.
Does higher resolution music equal higher level of involvement? That's one of those questions we have yet to answer.