Frequency and iconicity in ISL: Implications for acquisition

The Israeli Sign Language (ISL) is the major sign language of the Israeli Deaf community. The linguistic characteristics of the ISL have been studied in numerous publications (e.g., Meir & Sandler, 2008). However, little is known about ISL acquisition. This is the first study to explore vocabulary acquisition in the sign modality of bimodal-bilingual children acquiring ISL and Hebrew. The ISL lexicon is independent of that of Hebrew, and in many instances reflects semantic distinctions that are central to its community of signers (Meir & Sandler, 2008). Though the ISL is an independent language with its own lexicon and grammatical structures, most ISL users are bilingual (ISL-Hebrew). For the purposes of the current study, the ISL-CDI was adapted from the Hebrew-CDI (Gendler-Shalev & Dromi, 2017). The ISL-CDI presents 563 videos of lexical signs. Based on the Hebrew-CDI, changes for modality and language specific properties were made. For example, body parts which are signed using pointing and non-sign gestures were excluded, similarly to other sign CDI versions. ISL synonyms for a single lexical Hebrew entry were included if both were judged to exist in ISL child-directed signing. Some Hebrew lexical entries that do not have ISL correlates were excluded from the list. The study assessed the effects of iconicity and frequency on early lexicon development. Previous research brings inconclusive evidence on the effects of iconicity and frequency in sign language acquisition (Thompson, Vinson, Woll, & Vigliocco, 2012; Caselli & Pyers, 2017). During the first stage, iconicity and frequency ratings were collected. Thirty-nine sign-naïve adults completed an iconicity-rating task (on a scale of 1-7). The iconicity ratings varied between 1.2 and 6.9. The results showed that 56% of signs in the ILS-CDI were rated as highly iconic (greater than a 4 on a 7-point scale). Twenty-two native signers of the ISL rated the frequency of signs on a 1-7 scale. The frequency ratings varied between 2.2. and 6.5. The results showed that 95% of signs in the ILS-CDI were rated as highly frequent, i.e. greater than a 4 on a 7-point scale. During the second stage, we collected data from 20 bimodal-bilingual children who acquire ISL as their native language. The children`s ages ranged between 1 and 3 years old (and few older children who present ceiling scores on the test). The ISL-CDIs were filled by their parents; the Hebrew-CDI was completed by pre-school teachers or speech and language pathologists. Background data were collected via parental questionnaires. First, the results indicated a developmental trend: children`s vocabulary in ISL steadily increase with age. Second, a binary logistic regression was performed to ascertain the effects of iconicity and frequency on the acquisition of signs. In younger children (aged 8-40 months), age was found to account for 12% of the variance, frequency - 5.8%, iconicity - 0.7%. Thus, the results for the current study demonstrate that frequency plays a bigger role in sign acquisition than iconicity.