“…The empirical evidence collected in English, French, Spanish, Farsi and even Amharic (national language of Ethiopia) shows that congenitally deaf children who were exposed to CS from their earliest months by their parents and other caregivers can reach levels of mastery of spoken (phonology, lexical, morpho-syntactic) language and written language (word reading, reading comprehension, spelling) within range of age-matched hearing peers when tested at school age. Children with late and less intensive exposure (i.e., at the age of 5–6 years, and at school only) do not demonstrate the outstanding phonological and reading abilities of the early CS-users, confirming the existence of a sensitive period for language acquisition via the visual modality (Nicholls and McGill, 1982; Périer et al, 1990; Charlier and Leybaert, 2000; Leybaert, 2000; LaSasso et al, 2003; Torres and Moreno-Torres, 2006; Koo et al, 2008; LaSasso, 2010; Movallali, 2011; Heracleous et al, 2012; Colin et al, 2013; Rees and Bladel, 2013; Shull et al, 2016). …”