I’m trying to simplify this as much as possible, yet treading on the razor edge of PC.
I know that the term “mentally-challenged” can refer to many different types of deficiency, but I’m assuming that there are certain syndromes and patterns that can be identified. So my question is: are there types of mental deficiencies that would parallel the brain of a healthy non-human animal? For example, are there human brains whose functions approximate those of chimps, or types of monkeys, or pigs, or cats, etc. Or do the brains of these animals differ qualitatively to the extent that no comparison is possible? And of course, do species-specific instincts override these similarities?
If somebody wants to re-word this to make more sense scientifically, please do.
I’ve heard that chimps are equivalent to (very strong) two- or four-year-old humans. (No cite, going on vague memory, YMMV, does not include documentation and destination fees, etc.) If that is true, then one might say that a developmentally-delayed human who is ‘like a three-year-old’ might function like a healthy adult chimp.
If I understand your question, then I believe the human brain is wired differently.
For example, in his book The Dragons of Eden Carl Sagan mentions a form of mental retardation in which people’s brains are roughly the size of an adult chimpanzee. The people are mentally retarded, but they speak fluently. Language is apparently hard-wired in humans deeply enough to persist even over brain size issues.
They only use that term “equivalent” to mean certain human mental functions. A healthy adult chimp is a lot smarter than a human 2-year old in many respects. One being that a 2 year old human is unable to survive on its own.
As for the OP, I don’t think so. Any healthy animal, like my example above, is able to survive on its own (or, if social, without any special treatment from the group). A human has to be severely mentally challenged to have no language capability, and almost all humans have at least some language capability.
It’s tempting to think of some animals as just humans that are developmentally delayed, but they are fully formed as members of their own species.
There is only the barest equivalence between retarded humans and healthy animals. It’s a popular, but a terrible analogy in getting grasp on mental functioning differences. Anmals are not retarded or infantile humans.