For all heritage language learners, Kondo-Brown suggests that proficiency is positively correlated to both a strong perception of heritage and ethnic identity and a strong community in one's ethnic group.[22] Much research backs this claim.[23][24][25][26][27] In a study of Japanese heritage language learners, Kondo-Brown found that individuals with one parent speaking the language performed much better in both grammatical knowledge, and various self-assessment tools than those without a parent speaking Japanese.