This dissertation wants to deliver an original contribution to the existing national and international Sign Language Acquisition and Assessment research, mainly in four domains:

First, the exploratory case study is the first detailed description of a moderately deaf child’s Flemish Sign Language development, with native exposure to Flemish Sign Language (VGT) from birth up to the age of 24 months. Remarkable linguistic and interactional phenomena – e.g., lexical development, pointing behavior, visual communication strategies, and child-directed signing – were highlighted and discussed along with a longitudinal description of the child’s (pre)lingual contributions to the early parent-child interactions by means of Halliday’s Systemic Functional Theory (1975b), and confirming Halliday’s claim on the universality of the developmental order of his children’s functions of language.

Second, this research examined the parental use of visual communication strategies in more detail using van den Bogaerde’s strategy of attention classification (2000). The parental strategies to ensure that the child sees language were described within 10 parentchild dyads and their interactions were analyzed by applying a combined longitudinal and cross-sectional research approach. Differences in parental use were found and could be attributed to parental hearing status and gender. The use or non-use of particular strategies was found to influence the successfulness of these early interactions.

Third, these previous findings substantiated the development of the first Flemish Sign Language assessment for 6- to 24-month-old VGT sign-exposed deaf children. This research thoroughly described the adaptation process of the original American Sign Language VCSLchecklist (Simms et al., 2013) to Flemish Sign Language. Even though the standardization of the VGT VCSL-checklist is ongoing, the effectiveness of the adapted assessment could be proven based on cohort-differences associated with the three different cohorts’ linguistic backgrounds; i.e. parents provided their child with native, early or no VGT input.

And fourth, cross-linguistic research uncovered similarities and differences between the newly adapted VGT VCSL-checklist, the original ASL VCSL-checklist and the strict ASL norms. Most remarkable was that no basal age – i.e. the age level at which the child has mastered the previous (less mature) assessment items – could be found for the 3 VGT signexposed deaf children of hearing parents. Hence, this dissertation also stresses the need for long-term sustainable support for new (hearing) parents of deaf children and the introduction of deaf role models in the life of deaf sign-exposed children.

It was of great importance to develop the first diagnostic instrument for Flemish Sign Language, because to date close monitoring is non-existent. The VGT VCSL-checklist finally enables early interventionists and SLP’s to document and monitor sign-exposed children’s early visual communication and Flemish Sign Language development and progress until the age of 24 months. The checklist should be seen as part of a multi-modal approach in which deaf children’s language repertoire can be assessed in all languages, spoken and signed. This close monitoring can lead to early and fast result-based interventions and the improvement of the quality of specialized and individually oriented therapy targeting the child’s visual needs. It can further also help parents to ameliorate their child’s language input and the dyadic early interactions, and thus it can support sign-exposed children’s early natural development of Flemish Sign Language and optimize the child’s visual language input.