In the fourth lecture, we returned to behavioral studies that have attempted to inculcate even a rudimentary symbolic Combinatorics system in primates and parrots. Analysis shows that these animals' skills remain very limited in the syntactic domain. Their learning seems to be based on the memory of specific combinations of words or symbols, rather than on a genuine generative grammar. The contrast with the human species is striking: whether in the domain of words or in that of logical rules, humans, including young children, quickly learn to discover the general rules that govern a domain, a skill that exceeds that of macaque monkeys or chimpanzees.
In a review article published in Neuron, we proposed a five-level classification of the mental representation of sequences: knowledge of temporal transitions from one item to another (Markov chains), formation of groups(chunks), encoding of numerical order, abstract algebraic patterns (e.g. xxY, a repetition followed by a different item) and finally embedded tree structures, typical of human languages (sentences formed of recursively embedded syntagms). The analysis suggests that the first four levels are accessible to other animal species such as the macaque or even the rat. On the other hand, there is no evidence, at least for the moment, that the fifth level is accessible to animals other than the human primate.
