What we have found to be effective for working around localized sensory dysfunctions is a way of webbing together different stimuli which individually address different senses. We can hope to get more sophisticated in our ability to localize cognitive problems so that the web of nexi is similarly self-healing to work around a particular problem. Thinking that cognitive difficulties can be expressed by a single dimension of dumbing down is a comparable oversimplification. For those without language difficulty, it is hard to tell reality from this dangerous oversimplification. To discover an affordable mesh of encodings that works around most of the actual problems, we will have to be more analytical, and discover how to isolate and work around different kinds of dysfunction.
Cognitive function is as rich and diverse a domain as sensory function.