To conclude, the behavioral data, together with the P2, provided evidence that Dutch-Cantonese bilinguals used the segment as the primary unit of planning during Cantonese speech planning. The results of the present study are compared to previous studies. However, a direct comparison with the present study was not possible due to task differences and participants' different language experiences. For example, we reported earlier ERP evidence during the lexical accessing stage for segmental processing than previous research with unbalanced bilinguals, who are less proficient in an alphabetic language (Qu et al., 2012; Yu et al., 2014). Our results have been interpreted and discussed within the existing literature and theories. In future research, a more direct comparison is preferable. Specifically, our proposal that proficiency of bilingual speakers in one language can modulate the adaptive behavior of processing unit in another certainly needs corroborative evidence from studies that tap directly into the effect of proficiency level on phonological encoding, preferably with planned comparisons of processing patterns in different languages within the same bilingual populations. In this way, further insights into the cross-linguistic functional unit(s) of phonological planning can be obtained. Future endeavors should also explore whether a timing difference can be shown between segmental and syllabic activation within and between Germanic and syllabic languages. To conclude, the language background of bilinguals can have a significant impact on the primary processing unit during speech production in a specific language.