Children and Declarative Knowledge
Dr. Reber notes that young children acquire huge amounts of information "relatively independently of conscious attempts to acquire it and without much in the way of conscious knowledge of what they have learned", sometimes much better than older children "who tend to engage in more explicit-type learning." However, it seems that older children do better on "the explicit task." Reber, Implicit Learning and Tacit Knowledge, 1003, pp. 94-97.
This is certainly in line with Shh Tract's claim that language is not necessary for cognition and can actually interfere with cognition. And that explicit learning (although "supported by conscious strategies for acquisition" (Ibid, p. 97) is not cognition at all. The basic fact is this: Explicit learning does not add to our procedural, or tacit, store of knowledge. It only adds to our "declarative knowledge." Declarative knowledge can be tentative knowledge gained by attempting to identify what is stored in our own cognitive unconscious, or it can be tentative knowledge borrowed from other people. But if "cognition" is our own personal knowing of "the outside world" (Shh Tract), explicit learning adds nothing to what is already in our cognitive unconscious..
American kindergartners readily learn Mandarin (See "Mastering Mandarin", San Francisco Chronicle, April 17, 2012). But it is almost impossible for adults to do so, probably because Mandarin has been rendered into English ("pin yin"). Adults just don't (or perhaps can't) listen.