NACIMIENTO DE LA TEORÍA ARGUMENTATIVA CONTEMPORÁNEA

Significantly delayed onset of speech and poor intelligibility are two primary reasons for introducing Augmentative and Alternative Communication (AAC) to children with Down syndrome (Brady, 2008). The primary purpose of AAC is to increase opportunities for communication by providing an additional modality or by enforcing, supporting existing modalities through which individuals can enhance their communication with a variety of different people in their lives, such as parents, siblings, peers, and educators (Barker, Akaba, Brady, & Thiemann- Bourque, 2013). If children with Down syndrome are able to understand more than they are able to produce and if there is a way to bypass their speech production problem, they should become more effective communicators (Kay-Raining Bird et al., 2000; Kumin, 2003; Miller, 1999). Given that language learning takes place through communication and, as has been found in the present thesis in children with Down syndrome, is propelled by the communicative intent of a child (Kühn & Langner, 2012), providing different means for communication, such as manual signs, positively influences lexical development. Making words more perceptually salient by producing them in single-word utterances or final utterance position (Fernald & Mazzie, 1991), reducing the complexity of the utterance, providing clear cues as to the referent for a word (Hoff & Naigles, 2002), and using multi-

modal input all positively impacts novel word learning in children with Down syndrome (Kay-Raining Bird & Cleave, 2015).

Lexical development for children using AAC is also influenced by how adults model or shape the use of this augmented language (Romski & Sevcik, 2003), as is the case with learning to speak as well, which again shows the need for a communicative perspective on vocabulary learning. This augmented input supports the development by providing models of AAC usage, illustrating the usefulness, and demonstrating that it is an acceptable way of communicating. Augmented input illustrates the real-world meaning of symbols and signs, the many functions that they can serve, and it demonstrates that AAC is both accepted and encouraged as a modality for communication (Sevcik & Romski, 2002). Augmented, multimodal input is therefore recognized as an important ingredient for children to learn new vocabulary and to increase expressive and receptive language skills (Barker et al., 2013). In 6- to 8-year old children with Down syndrome, vocabulary levels were a strong predictor of social behaviour (Næss, Nygaard, Ostad, Dolva & Halaas Lyster, 2016). Receptive vocabulary predicted social problems, while expressive vocabulary predicted social capabilities. Næss and colleagues conclude that because vocabulary emerged as an important predictor of social functioning, lexical development should be the focus of early interventions for children with Down syndrome.

When children use multimodal forms of communication, as do most young children with Down syndrome, this has to be accounted for in the assessment of lexical development. The present thesis showed that the N-CDI is a valid measurement of multimodal vocabulary. The adapted version (see Chapter 2) can easily be used in clinical practice and is a cost- and time-effective way to gain insight in the size of the vocabulary of young children with Down syndrome. Next to the N-CDI, the functional use of words should be identified to gain insight in the way that children use their multimodal vocabulary in everyday communication. Analyses relating to determining core vocabulary (see Chapter 3) can be used as assessment method in clinical practice as well. Language sample collection and analysis is an historically used evidence-based practice for selecting vocabulary for speech-language therapy and AAC interventions (Kovacs & Hill, 2015). Vocabulary selection should be guided by two main principles: (a) the need to convey essential messages and (b) the eventual development of language skills (Beukelman & Mirenda, 2013). Selected vocabulary should be highly supportive of language and communication development because vocabulary development is key in language learning (Hohenberger & Peltzer-Karpf, 2009). Within the assessment of lexical development focus should be on both core and fringe vocabulary.

v

6

The present thesis has shown that the lexical development needs a communicative perspective. Professionals working with and parents of children with Down syndrome should become aware of all predictors and processes influencing the lexical development of these children. In speech-language therapy and AAC interventions, all these predictors and processes should be assessed and taken into account in clinical-decision making. Language and communication require interprofessional collaboration, since the present study showed that it is about more than only vocabulary and speech. In interprofessional collaboration several involved disciplines, in close collaboration with the child and/or family, formulate shared intervention goals, speak the same language, which is accessible and understandable for all involved, and perceive the qualities and perspectives of other disciplines as complementary and valuable (Buntinx & Bijwaard, 2004). Given the number and variety of internal and external predictors of lexical development, as identified in the present thesis, multiple disciplines (e.g., speech- language pathology, occupational and physical therapy, teachers, psychology/ behavioural and educational science) have to work together more closely. Involved professionals have to communicate more openly, both with other professionals as well as with parents. The ICF-CY provides a useful framework and the shared language needed for clinical practice to construct an integrative profile of lexical development and communicative performance, including body functions, structures, activities and participation, and environmental and personal factors (see Chapter 5). Intervention planning in children with Down syndrome should include this ‘whole person’ perspective. Professionals have to look beyond the borders of their own discipline and should integrate insights from colleagues into their clinical practice in order to create the best learning environments for children with Down syndrome to learn new words. Within a communicative perspective on lexical development, all communication partners in the social network of the child with Down syndrome should be involved.

Chapter 7