1 ARITHMETICAL ABILITIES IN BRAZILIAN DEAF SIGNERS OF ELEMENTARY SCHOOL Silene P. Madalena 1 , Kátia D. Silva 2 , Flávia Heloísa Santos 3 , Mônica Marins 4 1 Universidade Federal do Rio de Janeiro, Brazil; 2 Secretaria de Educação, Prefeitura Municipal de Teresópolis, Brazil; 3 Universidade do Minho, Portugal; 4 Universidade Veiga de Almeida, Brazil The present study investigated the effect of Sign Language acquisition period in deaf signaling students on their linguistic, arithmetic and cognitive skills. Participants were 58 students (24 female) with pre-lingual deafness enrolled from 2 nd to 5 th grades from Brazilian Institute for Deaf Students Education (INES). They were divided into two groups (early versus late) according to the age at the beginning of Sign Language acquisition. Standardized tests were applied: The Raven’s Progressive Matrices; School Achievement Test; Sign Language Assessment Instrument. The results were evaluated in both, quantitative and qualitative ways. Statistical analysis showed that children who learnt sign language before age four performed better in basic mathematical concepts and language skills. There was also academic progression throughout scholar levels in this population as a whole, regarding arithmetic knowledge and expressive language. Numerical Cognition is influenced by biological, cognitive, educational, and cultural factors (Santos et al., 2012), and involves three main systems: The Number Sense (NS) (Dehaene, 2009); the calculation (CA) itself, and Number Processing (McCloskey, Caramazza & Basili, 1985). At the beginning, numerical cognition development is universal and observed in infants as part of an evolutionary predisposition; gradually starting to vary according to mutual interactions and experiences (Dehaene, 2009; Hyde & Spelke, 2011; Starkey & McCandliss, 2014). The language has a role in the construction of cognitive abilities, and among them, those that are specifically mathematically-based (Göbel et al., 2014). According to Salillas and Carreiras (2014) exact arithmetic is acquired in a language-specific format as well as number concepts. In addition, language areas are activated during some numerical tasks. This could be observed by the use of specific Sign Language strategies as the signed algorithm (Nunes & Moreno, 1998). Hearing is an essential channel responsible for the oral language acquisition. Thus the hearing loss will interfere significantly in the interdependent language processes such as: thought development, memory, concepts in number, measurement, operations and problem solving, and patterns, reasoning, among others especially for those born or become deaf in the pre-lingual period (Pagliaro & Kritzer, 2013; Pénicaud et al., 2013). Around 90% of deaf children belong to listener families (Silva, Pereira & Zanolli, 2007), which usually cannot offer a favorable linguistic environment to develop the Sign Language. Unfortunately, the time relapsed between hearing loss detection and initiation of appropriate care in Brazil is still high (around three years), which further compromises the children possibilities for acquiring oral communication (Silva, Llerena & Cardoso, 2007). In contrast, deaf children whose parents are deaf users of Sign Language develop their communication earlier, being able to perform as well as the hearing children (Quadros & Cruz, 2011). Thus it seems inappropriate to associate the deaf children’s cognitive level to their language skills. The Brazilian Sign Language (LIBRAS) was recognized as an official language in Brazil since 2002. In the few bilingual deaf schools available in the country, the Sign Language is the main language of education, and the children enter at the school with different levels of Sign Language proficiency. Our previous results revealed the presence of heterogeneous mathematics performance levels for students in the same scholar grade (Madalena, Marins & Santos, 2012). Nevertheless it was not clear if language performance could explain those differences. The present study aimed to explore the relationships between the period of Sign