The role of oral components in Italian sign language comprehension

What is the role of oral components in sign language? To shed light on such a controversial phenomenon, an experimental test was designed and disseminated online. It involved over 273 deaf and hearing signers from all over Italy. The purpose of the test was to provide quantitative data on the role that the oral components plays at the lexical level of LIS (Lingua Italiana dei Segni/Italian Sign Language), to supplement the observations that have been made in qualitative studies of LIS and other sign languages. The results show that deaf participants recognise, more than hearing ones, signs where the oral component is obscured, confirming their higher proficiency in sign comprehension probably due to their larger vocabu- lary knowledge. Moreover, deaf native signers provide a significantly higher number of correct answers than non-native deaf signers. The same is not true for hearing participants, who do not differ according to being native or non-native signers. In general, the results confirm that mouthing has a distinctive disam- biguating function at the lexical level, which leads us to conclude that mouth actions have a constitutive role in LIS and should not be considered an extralinguistic phenomenon, as had been assumed in older traditional linguistic descriptions of this language.