Discussion

This study explored feedback from hearing parents of DHH children and NGT teachers on the ZINinNGT prototype—an NGT learning app for parents focused on sentence formation. While participants provided detailed feedback on specific features, several broader themes emerged that can inform both the future development of ZINinNGT and other sign language learning tools.

Validation and extension of design principles

In this section, we discuss the original design principles presented in Sect. 3.1 and extend them based on insights gained from our user study.

First, our findings reinforce the importance of going beyond the vocabulary level in sign language materials. Both parents and teachers viewed the app’s focus on full sentences and grammar explanation as a key strength. This aligns with earlier research showing that hearing parents wish for more instruction on sentence structure in sign language courses and resources [14–16]. The use of a literal sign-for-sign translation, with highlighting of the currently produced sign, was seen as effective in making sentence structure more transparent. These findings suggest that future tools should focus on supporting broader language development rather than focusing solely on vocabulary learning.

Second, several features that enabled perceptual control were viewed very positively. Participants appreciated the adjustable playback speed, multiple camera angles, and different subtitle options, all of which were seen as helpful for learning.

Third, the possibility to use the search bar, mark videos as favorites, and filter by semantic theme were considered helpful in content retrieval. More broadly, this highlights the principle of need-driven retrieval: parents valued being able to quickly find the content most relevant to their learning objectives or daily communicative needs.

Fourth, many parents expressed a desire for a more holistic app—one that includes sentences and grammar explanation, but also lexicon and quizzes. They preferred a single platform where they could study grammar, look up signs and practice what they had learned. This also underscores the importance of interactive activities, such as quizzes, aligning with the Multiple pedagogies/activities principle described by Jamaldeen, Hewagamage, and Ekanayaka [29] and with other previous literature [30].

Fifth, parents missed design features related to stimulating learner motivation. They expressed a wish for gamification elements, again aligning with the guidelines of Jamaldeen, Hewagamage, and Ekanayaka [29] and other research that emphasizes the importance of implementing gamification to increase learning motivation and perseverance [30, 31].

Sixth, teachers emphasized the need for a visual-first approach. A sign language app for parents should keep text to a minimum, matching the visual nature of sign language and making it more accessible for parents from different language backgrounds.

A seventh key theme was the tension between standardization and natural variation in NGT. While the app intentionally aimed to reflect sign language as used within the Deaf community, some participants expressed confusion when signs or grammar differed from what they had previously learned. This raises a broader question for sign language learning tools: should they prioritize standardized forms for consistency, or embrace variation to reflect natural language use? A possible middle ground is to explicitly acknowledge variation—for example, by including sign variants and an explanation of natural variation—so that learners gain awareness without becoming confused. It is also important to note that sentence-level signing involves more variation than individual signs, and there is no one-to-one correspondence between written sentences and their signed equivalents. The goal of a sentence-focused tool should therefore not be for parents to memorize full sentences, but to develop the ability to form their own, which can be difficult to achieve without teacher guidance. Language learning apps should be viewed as a supplement to language courses rather than a replacement thereof. As found by Jamaldeen, Hewagamage, and Ekanayaka [29], mobile language learning tools are less effective when used as a primary means of learning rather than being integrated in a broader learning environment.

Lastly, several parents mentioned that they imagined using ZINinNGT together with their child. While ZINinNGT was not designed for young children (it lacks fun images, colors, and games), this feedback reveals a clear interest in material that can be used together by parent and child. This aligns with findings reported in our previous publication [16], in which we found that parents and teachers value self-study resources that can be used for joint parent–child learning. Future tools may benefit from incorporating elements attractive to children to support joint sign language learning between hearing parents and their DHH children.

In summary, based on the results of our user study, we validated our original three design principles and extended them to the following eight:Grammar-aware input;Perceptual control;Need-driven retrieval;Holistic design;Design for learner motivation;Visual-first;Variant-aware;Joint parent–child use.

Limitations of the study

This section outlines several limitations of our study that may have influenced the findings and their generalizability.

First of all, the study focuses on design principles derived from a short-term user study. While design features can contribute to a productive and motivating learning environment, app design by itself does not ensure good learning outcomes [31]. With this study, we aimed to provide insight into the design principles required for sign language learning apps. However, the study does not provide insight into users’ learning trajectories nor the aspects that contribute most to learning gains (see [31] for suggestions for potential research questions when evaluating gamified language learning apps). Therefore, to gain a better understanding of the effectiveness of a language learning app, it would be largely beneficial to include second language learning frameworks and conduct a long-term evaluation study focusing on both learning experiences and objective learning outcomes. For example, this could involve conducting quantitative pre- and post-tests on various language skills, combined with user experience surveys or interviews. We plan to conduct such a study once ZINinNGT is ready for public use.

Second, our recruitment call was written in Dutch, and all interviews with parents were also conducted in Dutch. This, of course, implies that participants were fluent in the language. However, in the Netherlands, 12% of DHH individuals are first-generation immigrants and 20% are second-generation immigrants, reflecting large ethnic and linguistic diversity [39]. Teachers in our sample also mentioned large linguistic diversity amongst parents in their courses and therefore suggested making ZINinNGT less text-heavy and adding translations into other languages. Our parent participants did not raise language accessibility issues—likely because they did not reflect the diversity present in the broader population of parents of DHH children in the Netherlands.

Further, when asking participants about user intent, there is a risk that participants will respond positively to all new materials simply due to a general lack of sign language resources. Both parents and teachers expressed appreciation for new materials being developed, making it difficult to determine whether their enthusiasm was specific to our app or more broadly directed toward any sign language learning tool. Additionally, participants were aware that they took part in a study focused on a sign language app, which likely made them more open to the idea of an app—possibly more so than the average parent or teacher. Still, their explanations for potential use provide meaningful insights into the features they appreciated and the contexts in which they imagined using the app.

Finally, observing participants as they tried out the prototype is not representative of real-world app use. The presence of a researcher likely influenced participants’ behavior, and sharing their thoughts aloud may have felt awkward or unnatural to some, potentially affecting the authenticity of their responses.

Further development of the app

Based on the feedback from parents and teachers, we have been working on a new version of ZINinNGT that addresses the issues and wishes identified in our study. To create this new version, we collaborated with a Deaf-led company¹ that focuses on teaching and spreading information about NGT and Deaf culture. A first beta version of the app—now called Signio—was released in September 2025.² Signio is aimed at a broader target audience but will include a dedicated section for parents that is free to use and features example sentences and grammar explanation videos. At the time of writing, Signio has approximately 13,100 registered users. It is also possible to use the app without an account (but we do not have data on the number of unregistered users).

To create a more holistic learning tool (additional design principle 4), we expanded the app by including separate vocabulary, quizzes, and gamification elements. The quizzes currently focus on vocabulary comprehension, while the gamification features allow users to earn points, complete levels and track their progress, making learning more motivating (additional design principle 5), see Fig. 5.

Fig. 5: Screenshots of the new version of ZINinNGT showing gamification and a quiz question

To make the app more visual—and less textual—(principle 6), we redesigned the interface to include additional icons, increased use of color, reduced text, and a visual-first home screen.

In line with principle 7 (variant-aware design), we included both standardized and regional variants in the new vocabulary section and plan to add explanation videos on natural variation in NGT. By doing so, we aim to reduce parents’ confusion about the “correctness” of signs and increase their awareness of natural linguistic variation.

At the time of writing, the app includes 3,349 videos of example sentences specifically created for hearing parents of DHH children. Future plans include expanding the app to 4,300 videos of example sentences (all of which have already been recorded and subtitled), adding approximately 30–40 grammar explanation videos with topics particularly relevant for parents (such as getting attention, child-directed signing and use of conditionals) as well as videos on Deaf culture.

In addition, all sentences have also been recorded as 3D animations using motion capture technology, as we aim to use signing avatars to generate up to 10,000 sentence videos by making use of compositionality. This means that, by combining words or phrases, we aim to create new sentences from existing elements (for example, combining “Do you want an apple?” and “There’s a pear on the plate.” to generate “Do you want a pear?” and “There’s an apple on the plate.”) The use of 3D avatars also allows for a 360-degree view of the signing, as well as a zoom function to clearly distinguish different handshapes (see Fig. 6)—a solution to the difficulty of adding handshape information to full sentences.

Fig. 6: Screenshots of the new version of ZINinNGT showing an avatar from different angles

To further enhance engagement and support joint parent–child learning, we plan to incorporate videos of stories in NGT signed by both human and virtual signers, including cartoonish or non-human characters. For children, it is especially important to create an engaging and interactive learning environment [42]. Moreover, research indicates that the use of colorful cartoon characters can stimulate children’s curiosity, thereby enhancing engagement and facilitating language learning [30]. By visual enhancements and by integrating quizzes, a structured learning path, NGT stories, and cartoon characters, we aim to make the app appealing to children and support joint parent–child learning (design principle 8).

Lastly, Jamaldeen, Hewagamage, and Ekanayaka [29] identified the incorporation of collaborative activities as a core facet of mobile learning design. Wiboolyasarin and Jinowat [30] also identified collaboration—besides personalization, interactivity, and gamification—as one of the design features that are most effective in enhancing the language proficiency of primary school children. In the Signio app, different thematic collections are integrated, and users can create and share their own collections. The ability to create personalized collections contributes to the need-driven retrieval and personalization of the app, while sharing collections may be seen as a first step towards collaboration. Although not identified as a separate design principle in this study, adding actual collaborative activities to the app may be beneficial—especially when aiming to make Signio attractive to children.

Footnotes

1. See TYD | Nederlandse Gebarentaal voor iedereen [40]. ↩

2. For more information and download see Signio-app—Leer Nederlandse Gebarentaal [41]. ↩