Jean-Philippe I follow your presentation without any difficulty until you arrive at the final line where you state, "For gestures, we might have a doubt and imagine it is only mimicking but language is an example of modeling" I doubt very, very much that language acquisition can be accounted for by modeling alone. Yes, of course, there is a strong experiential component and that is driven by modeling. However if you examine the degraded nature of the input (what adults actually say in the presence of the children that are attempting to master that language), then I suspect that you would come quickly enough to appreciate that to extract from this degraded input a complete operational grammar of the language is is bit more than a tad beyond belief - thus, the importance of the proposals such as the language organ and universal grammar. These are attempts, either originated or promoted by Chomsky, to account for this enormous gap between the degraded output of adults and the amazing accomplishment of every member of our species with a testable IQ (this is patently NOT an endorsement of that nonsensical "measurement" but a point in a presentation) in coming to a tacit and completely operational mastery of the language so presented. As crucial (and compulsive) as modeling is to our species, it requires the existence of a pre-set neurology (the human LAD - language acquisition device) to achieve this task - that of language acquisition. All the best, John