  Neither of these explanations of the KE's seems especially congenial  to the linguistic nativist. For both tacitly assume that language  learning, including syntactic learning, is not (or not entirely)  subserved by special-purpose mechanisms. Rather, it is mediated by  more general motor circuitry (according to the Vargha-Khadem  hypothesis) or reward-based learning and working memory abilities  (according to Lieberman) that are also involved in other learning  tasks.