This is an excellent video by Joe Casey (DPE) on Spatial Disorientation. Some of the illustrations and techniques in this video are eye opening. Ways to show the effects of SD and ways to avoid SD begin about halfway through the video (see they guys spinning with the bats - LOL). Enjoy!
I found his comments about "putting the vestibular system on another axis" to be a good way of explaining what is happening. Even in VFR conditions a pilot looking inside with his head down during a turn can become disoriented. In VFR conditions the view outside can quickly correct this. The acceleration/deceleration effects are known to most pilots but still it's interesting to learn not only what is happening but why it is so. Most of you IFR guys are likely way beyond most of this having learned it a long time ago. But I'm in awe of how them airshow aerobatic pilots keep it together ... without blowing chow!
