Measuring language dominance in bilinguals of two sign languages

The research question asked here is whether the construct of language dominance in the spoken modality is cross-modal and quantifiable in sign languages. Sign languages have been described as similar due to their visually iconic nature, drawing from similar sets of gestures used in different cultures, thereby leading to the question of whether the similarities can greatly facilitate the acquisition of a second sign language by a signer who already knows a sign language beforehand. To answer this question, I used a self-report assessing language dominance, the American Sign Language Bilingual Language Profile (ASL-BLP), which was validated by a phonological fluency task in the signed modality. Fourteen sign languages were represented in this study, with American Sign Language (ASL) being a common sign language for all the participants. The ASL-BLP produced a global dominance score for each participant based on questions about years of use, the average week of use in different domains, proficiency levels, and language attitudes. The same questions were asked about both languages. In the phonological fluency task, participants generated signs in both their sign languages based on phonological cues in the signing modality, namely three handshapes, one location cue, and one movement cue. The proportion of signs generated in ASL correlated with the global dominance scores obtained from the ASL-BLP, suggesting that at least in terms of lexical processing, the acquisition of a second sign language is a long-term process relatively unaffected by iconic properties of sign languages. The construct of language dominance in the signed modality may have implications for professionals providing treatments in health care and accommodations in educational settings to bilinguals of two sign languages