"A heritage student is a student who is raised in a home where a non-English language is spoken, who speaks or merely understands the HL, and who is to some degree bilingual in English and the other HL" (Valdez, 2001, p.3 8).
Most of the early Chinese immigrants to the U.S. came from Gwongdung (Guangdong) Province during the Gold Rush, most notably from a coastal county known as 新寧 (modern-day Taishan). Many of them settled in San Francisco and formed a community known as 唐人街 (Tang People Street) in Cantonese and Chinatown in English. By 1960s, Taishanese still made up over 60% of the Chinese immigrant population in the U.S. An example of a famous Cantonese American of Taishanese descent is former ambassador to China Gary Locke.
Bases on Valdez' definition, a CHL learner "is raised in a home" where Cantonese is spoken. The learner can speak or understand Cantonese to a certain extent.
My colleagues and I have found general trends when we focus on CHL learners who are the second generation of Cantonese immigrants (Dennig & Leung, 2012a, 2012b; Dennig, Leung, & Uchikoshi, 2011):
Variability is fact part of any form of language learning. Research on L1 acquisition by monolingual children has increasingly found individual differences, not just in the acquisition of vocabulary and complex structures, but also in basic grammatical structures (Dąbrowska, 2013). Variability is to be expected in CHL learning as CHL learners are more influenced than their monolingual peers by a synergy of social factors, e.g. availability of Cantonese in their school systems, societal attitude towards Cantonese, and the social context in which they use Cantonese. The social factors combined with their personal experience with speaking Cantonese help shape their cultural identity, which influences how motivated they are about maintaining their HL.
About three-quarters of the adult CHL learners in our research project were administered ACTFL's Oral Proficiency Interview and their proficiency levels ranged from intermediate-low to advanced-mid, which is consistent with my observation about the CHL learners in my Cantonese program. Being able to reach these levels is impressive. According to a report published in 2010 by the Center for Applied Second Language Studies (CASLS) at the University of Oregon, only a small percentage of FL students can reach the intermediate-mid level after four years of learning a FL: "Of course, the number of hours needed to reach a specific proficiency level varies from student to student, but our research shows that only about 15% of students reach a proficiency level near Intermediate-Mid even after approximately 720 hours of study, which is about four years in a typical high school program" (CASLS, 2010, p.1).
HL learners are indeed valuable human resources to this and other countries: "We desperately need competence in languages-to become "a language-competent society," in Tucker's phrase (1991)-and our huge and varied heritage language resources have a definite role to play in achieving such competence" (Fishman, 2001, p. 95).