One of the most fundamental, yet often neglected, or even paradoxical questions in the field of language acquisition is how children who have not yet acquired stable grammar can process language and still manage to acquire new grammar. This question is further complicated by cross-linguistic differences, such as how English- and Japanese-speaking children process complex sentences in their respective languages. To answer these two intricate questions, we need to identify cross-linguistically common – possibly universal or quasi-universal – characteristics in terms of the development of language processing strategies. At the same time, we also need to know whether different language processing strategies are used by children who speak different languages. We thus need to take both developmental and cross-linguistic issues into consideration simultaneously.