Processability Theory (PT) is a theory to explain the developmental course of the acquisition of L2 (second language) or other additional language. Although several language acquisition studies have supported PT validity, data from Dyson (2009) showed some counter evidence with Mandarin speaking ESL learners. In her study, the two participants showed a developmental course different from PT. However there is a problem in PT methodology. Furthermore, the course shown by Dyson revealed the possibility that the learners acquire the target structures of syntax and morphology separately. Through testing PT validity by reanalyzing Dyson’s data, the current study also reveals problems with “implicational scaling” used in a developmental study.