In their keynote contribution, Truscott and Sharwood Smith offer a general model of language development from a processing perspective. As they state, their model is very ambitious: Their ‘acquisition by processing’ theory (APT) aims not only at explaining both first and second language acquisition but also real-time processing in language comprehension and production. APT takes a cross-disciplinary approach that intends to bring together research on linguistic structure and on general cognition. However, the joint contribution of linguistic and psycholinguistic approaches is mainly evident in terms of theoretical concepts (e.g. UG, syntactic rules, modules, activation) because the presented empirical evidence is limited in scope.