This paper investigates English-speaking children's acquisition of raising constructions (e.g. "John seems to Mary to be happy") and fnds an asymmetric effect of NP type on their comprehension: an improvement in performance is observed when a lexical NP is raised across a pronominal experiencer (e.g. "John seems to her to be happy") compared to when a pronoun is raised across a lexical NP experiencer (e.g. "He seems to Mary to be happy"). These results are consistent with a processing-based approach to intervention effects, which reduces children's diffculty with raising to a performance limitation, rather than a grammatical defcit