Is there an interface between explicit and implicit knowledge in L2 acquisition? Rick de Graaff's doctoral dissertation tests this question in an experimental study from a weak interface position. This position indicates that explicit knowledge has a facilitative role in the acquisition of implicit knowledge when it engages the attention of learners and makes them notice input features (Schmidt, 1990). De Graaff studies the effect of explicit computer-aided self-instruction on the acquisition of morphosyntax in Experanto (an artificial language, based on Zamenhoff's Esperanto) and Spanish (as a foreign language) by adult native speakers of Dutch. Acquisition is tested in interaction with five intervening factors that constitute a controlled linguistic, psychological, and pedagogic context (i.e., complexity of structures, rule-based learning in syntax and exemplar-based learning in morphology, familiarity with the structures, availability of explicit knowledge, and learners' aptitude). Experanto is chosen to control for the influence of previous knowledge and contact outside class, and Spanish is chosen to make the results more generalizable.