It's an open question. I just don't know if that is the case and I'm very curious to know more about this. The chimp-human example is very convincing. Further someone with down-syndrome probably cannot understand what you can comprehend. So where is the gap, is there one? It looks like. This says, yes, I should believe what the SIAI claims. However, the original quote claims that "the most difficult subjects can be explained to the most slow-witted man". If this was the case, it would hint at the possibility that superhuman AI would merely be superhuman fast and had superhuman memory and ram, yet wouldn't reside on a different conceptual level.