Table 3 Methods, main outcomes, and methodological score of reviewed studies

Deckers et al., 2017 [61]

Cross-sectional study

Spontaneous language samples of 30 Dutch children with DS were collected during three different activities with multiple communication partners (free play with parents, lunch- or snack time at home or at school, and speech therapy sessions). Of these children, 19 used multimodal communication, primarily manual signs and speech. Functional word use in both modalities was transcribed. The 50 most frequently used core words accounted for 67.2% of the total word use; 16 words comprised core vocabulary, based on commonality.

The 50 most frequently used core words accounted for 67.2% of the total word use; 16 words were determined to be core vocabulary based on a commonality criterion. Words in the core vocabulary of young children with DS appear to be similar in syntactic semantic and pragmatic functions to core words identified by research in other populations, although the contribution of content words to the core vocabulary of the children with DS seems higher than in other groups.

Lorah, 2016 [38]

Experimental

Using an alternating treatment design, teachers and paraprofessionals were instructed to conduct mind training trials using both a PE system and an iPad® Mini with the application Proloqu2Go™ as an SGD, with seven school-aged children with a diagnosis of autism or DS. Following 10 weeks of data collection, the student participants were exposed to a device preference assessment, and teachers completed a social validity questionnaire to assess preference.

The results were consistent with previous research indicating equal acquisition and fidelity of use across both devices, but a general preference for the iPad®-based SGDs.

Lanter et al., 2016 [59]

Case report

The intervention describes how environmental arrangement and generalized cues were used to promote spontaneous communicative attempts during a reinforcing social-communicative context and explains how prompting and modelling were used to facilitate the performance of effective communication behaviors across multiple requesting opportunities.

The child showed significant increases in his use of functional communication, with collateral gains in speech, as demonstrated by the performance of requests.

González et al., 2015 [68]

Experimental

The methods and techniques included prototyping, questionnaires (pre–post), thinking out loud, video-recording, and structured observation. In terms of the interaction aspects with the whiteboard, the items evaluated included (a) mouse use, (b) placement of numbers and balls, (c) ball deletion and crossing out, (d) placement of the sign of the operation, and (e) use of sensitive areas established in the worksheet.

The use of the digital board (Divermates – prototype) facilitates the process of interaction and usability, and the attractive design that has been evaluated by the specialists enables it to be adapted to needs related to language, color, font size, use of metaphors, organization, presentation, grouping, and categorization of items. Due to the difficulty in writing, the picture has advantages, since it allows it to be operated with the hand and the difficulties with traditional writing can be forgotten. About subtraction and addition operations, the study population shows that subtraction is more difficult than addition. Participants needed help with fingers and balls (symbolic management) in the numerical counting process (task resolutions).

Logan et al., 2014 [57]

Case report

Report involving a 13-month-old girl (Natalie) over a 28-week period including 3 evaluation moments: baseline, intervention, and retention. The evaluations were carried out at home with the following schedule: 6 bi-weekly visits for 3 months (baseline), 12 weekly visits for 3 months (intervention), and 4 weekly visits for 1 month (retention). Natalie and her family were recorded in the video during the 28-week study using their ride on car in their home and in the community.

Ride-on car use appears to be feasible, fun, and functional in increasing daily mobility for pediatric populations working toward independent walking.

Wilkinson & Mcllvane, 2013 [52]

Experimental

Visual perceptual factors such as velocity and precision were evaluated by means of a search task, involving targets that were exposed in different spatial dispositions and internal color in one, with the symbols being grouped by internal color; in the other, the identical symbols had no scheme of agreement.

The visual search was superior in participants with ASD compared to those with DS. In both groups (ASD vs DS), responses were significantly faster when symbols were grouped by color. These results show that the visual and perceptual characteristics of the display may be essential characteristics to be considered during the display construction (device panel).

Hu et al., 2013 [64]

Experimental

This paper reports an empirical study that investigated the use of three input techniques (keyboard and mouse, word prediction, and speech recognition) by children and young adults with DS and neurotypical children.

Children with TD achieved better performance than participants with DS. The results suggest that some individuals with DS have the skills to enter text at a productive speed and with acceptable accuracy while others are very slow in entering data and the generated text contains a substantial number of errors. The DS group showed a greater variation than the neurotypical group in terms of data entry speed and accuracy.

Brady et al., 2013 [37]

Longitudinal

These 93 children were assessed at Time 1, followed by 82 of these children after one year being assessed at Time 2. They were exposed to different types of AAC, which were selected by teachers from a list of options, and teachers were asked to record all types of AAC in use for a particular child. Many children have been taught to use multiple forms. Many children added or changed systems throughout this study (therefore, analyses related to specific types of AAC were not possible).

Interventions using symbols by visual image, signs (gestures), and spoken words that may aid in cognitive development and language comprehension (ISF). This hypothetical ISF model reflects positively, since children showed higher levels of ISF, especially those with direct participation of adults at home (domestic environment).

Barker et al., 2013 [36]

Longitudinal

We developed two surveys (a) to describe children’s use of AAC in preschool classrooms, as well as the use of prompts and question asking, and augmented input by their communication partners; and (b) to describe teachers’ experience, training, and perceived support in providing AAC. We then examined the relationship between children’s experience of AAC, including the use of prompts, question asking, and augmented input by their partners, and the growth of receptive and expressive language for 71 children with developmental disabilities over a two-year period.

It is possible to observe positive effects in the use of PECS and SGDs, since they aid in the production of speech, language expression, and social communication of children with DD. The PECS is the form of AAC most used by schoolchildren. It was observed that more than half of the teachers received vocational training in PECS, while only 25% of the teachers had training in the use of SGDs.

Van Der Meer et al., 2012 [35]

Longitudinal

We compared speed of acquisition and preference for using SGDs versus manual signing (MAKATON) as AAC options. Four children with DD, aged 5–10 years, were taught to request preferred objects using iPod®-based SGDs and MAKATON. Intervention was introduced in a multiple-probe-across-participants design, and SGD and MAKATON conditions were compared in an alternating-treatment design. A systematic choice-making paradigm was implemented to determine whether the children showed a preference for using SGDs or MAKATON.

All participants showed increased use of SGDs when intervention was introduced, but only three learned under the MAKATON condition. This study shows that individuals with DD often show a preference for different AAC options, and it is important to consider the individual’s preference, as this can be an influential factor in communication skills, communicative function, and ease of acquisition.

Allsop et al., 2011 [55]

Observational

An interactive web-based survey was developed that stored information within a central database. The survey interface was designed for 4–11-year-olds with and without disabilities. Common accessibility issues were identified using the Web Accessibility Initiative, and then an inclusive design approach was used to improve the usability of the survey interface. The joystick designs were displayed as rotating 3D objects in video clips.

All children could complete the tasks from the survey, although children with disabilities had higher completion times and most required a form of assistance from support assistants and/or sign language interpreters. The use of the web-based survey provided a novel means by which to involve children with and without disabilities in the design of assistive technology devices within a primary school environment.

Wilkinson et al., 2008 [51]

Experimental

Participants were asked to find a target line drawing among an array of 12. Line drawings represented foods (e.g. grapes, cherries), clothing (e.g. a red shirt, a yellow shirt), or activities (e.g. football, swimming). In one condition, symbols that shared a color were clustered together, creating a subgroup within which to search. In another condition, symbols that shared a color were distributed across the display, allowing each to appear individually.

Grouping symbols of the same color facilitated target location velocity (food, clothing, activities) for all participants in the survey and accuracy for younger children and preschoolers with DS. In the construction of the display design, the internal coloring of the symbols should be considered, especially when dealing with individuals with DS, assisting the visual and perceptual condition.

Foreman & Crews, 1998 [8]

Experimental

The study used a simple repeated measures technique. All children who participated were encouraged to learn to communicate 12 unique words: three verbal instructions alone, three through the symbol method (COMPIC), three through the signal method (MAKATON), and three through the multimodal method (symbol + sign + verbal). The four treatments (verbal, symbol, signal, and multimodal) were administered successively over four days, with interaction and sequence effects being controlled by a Latin square design.

The multimodal method and signal method resulted in significantly higher scores for all children when compared to the symbol method. However, it can be concluded that the multimodal method of instruction is the most effective way of encouraging children with DS (between the ages of 2 and 4) to communicate the names of objects, since it makes use of three auxiliary tools (verbal, symbol, sign).