We recently observed some profoundly interesting eating behavior in groundhogs. A juvenile groundhog and its mother were grazing together. The mother started eating a plant and the juvenile came over and ate some of it out of her mouth. It then went and ate a great deal of the same plant, which we had not seen it do before.
It is possible that this was all a coincidence, but it looks like the juvenile learned that this kind of plant was edible from its mother. This raises the issue of how herbivores, including horses, know what to eat? It also raises the issue of how animals know how to learn?
The eating issue is interesting because the number of different species of plants is enormous, so instinct alone cannot say which are edible and which are not. Instinct can provide general guidance, beyond which there must be some some sort of learning process. but the learning process itself must be at least partially instinctive.
Here I am reminded of Chomsky's theory of language learning in humans. He argues that infant humans learn language far to quickly for the process to be one of inductive inference, that is by generalizing broad rules from narrow instances. There are too many different possible languages that fit the infant's limited experiences.
This also rules out trial and error learning, which we do not observe. Trial and error may occur for specific words, but not for learning the language as a whole.
Chomsky therefore concludes that all human language has an underlying structure that is known instinctively. If so then the vast array of different human languages are merely local variants on this universal underlying structure. Thus the child is not learning language per se, rather just the local variant.
The same may also be true when horses, groundhogs and rabbits learn what to eat. The basic framework knowledge must be instinctive, supplemented by a learning process that is also grounded in instinct. This is just two examples of an instinct being a body of basic knowledge. The challenges are (1) how to figure out what that knowledge is and (2) how to express it using human concepts and language, which may be very different from the critter's concepts.