Somatosensory processing in deaf and deafblind individuals: How does the brain adapt as a function of sensory and linguistic experience? A critical review.

How do deaf and deafblind individuals process touch? This question offers a unique model to understand the prospects and constraints of neural plasticity. Our brain constantly receives and processes signals from the environment and combines them into the most reliable information content. The nervous system adapts its functional and structural organization according to the input, and perceptual processing develops as a function of individual experience. However, there are still many unresolved questions regarding the deciding factors for these changes in deaf and deafblind individuals, and so far, findings are not consistent. To date, most studies have not taken the sensory and linguistic experiences of the included participants into account. As a result, the impact of sensory deprivation vs. language experience on somatosensory processing remains inconclusive. Even less is known about the impact of deafblindness on brain development. The resulting neural adaptations could be even more substantial, but no clear patterns have yet been identified. How do deafblind individuals process sensory input? Studies on deafblindness have mostly focused on single cases or groups of late-blind individuals. Importantly, the language backgrounds of deafblind communities are highly variable and include the usage of tactile languages. So far, this kind of linguistic experience and its consequences have not been considered in studies on basic perceptual functions. Here, we will provide a critical review of the literature, aiming at identifying determinants for neuroplasticity and gaps in our current knowledge of somatosensory processing in deaf and deafblind individuals.

Signed languages - Unique and ordinary: A commentary on.

In this commentary on the article by Kidd and Garcia, we point out that research on natural signed languages is an important component of the goal of broadening the database of knowledge about how languages are acquired. While signed languages do display some modality effects, they also have many similarities to spoken languages, both in function and in form. Thus, research on signed languages and their acquisition is important for a fuller understanding of the diversity of languages. Since signed languages are often learned in contexts other than those of typical input, it is also important to document the effects of input variation; we also see it as critical that input be provided as early as possible from models as fluent as possible. Finally, we call for removing existing barriers to training and education for would-be researchers, especially those interested in working on signed languages. Importantly, we advocate for the recognition of signed languages, for signed language research, and for the empowerment of community members to lead this research.

Signed Languages: A Triangular Semiotic Dimension.

Since the beginning of signed language research, the linguistic units have been divided into conventional, standard and fixed signs, all of which were considered as the core of the language, and iconic and productive signs, put at the edge of language. In the present paper, we will review different models proposed by signed language researchers over the years to describe the signed lexicon, showing how to overcome the hierarchical division between standard and productive lexicon. Drawing from the semiotic insights of Peirce we proposed to look at signs as a triadic construction built on symbolic, iconic, and indexical features. In our model, the different iconic, symbolic, and indexical features of signs are seen as the three sides of the same triangle, detectable in the single linguistic sign (Capirci, 2018; Puupponen, 2019). The key aspect is that the dominance of the feature will determine the different use of the linguistic unit, as we will show with examples from different discourse types (narratives, conference talks, poems, a theater monolog).

Referring strategies in American Sign Language and English (with co-speech gesture): The role of modality in referring to non-nameable objects.

American Sign Language (ASL) and English differ in linguistic resources available to express visual-spatial information. In a referential communication task, we examined the effect of language modality on the creation and mutual acceptance of reference to non-nameable figures. In both languages, description times reduced over iterations and references to the figures' geometric properties ("shape-based reference") declined over time in favor of expressions describing the figures' resemblance to nameable objects ("analogy-based reference"). ASL signers maintained a preference for shape-based reference until the final (sixth) round, while English speakers transitioned toward analogy-based reference by Round 3. Analogy-based references were more time efficient (associated with shorter round description times). Round completion times were longer for ASL than for English, possibly due to gaze demands of the task and/or to more shape-based descriptions. Signers' referring expressions remained unaffected by figure complexity while speakers preferred analogy-based expressions for complex figures and shape-based expressions for simple figures. Like speech, co-speech gestures decreased over iterations. Gestures primarily accompanied shape-based references, but listeners rarely looked at these gestures, suggesting that they were recruited to aid the speaker rather than the addressee. Overall, different linguistic resources (classifier constructions vs. geometric vocabulary) imposed distinct demands on referring strategies in ASL and English.

Iconicity as a general property of language: evidence from spoken and signed languages.

Current views about language are dominated by the idea of arbitrary connections between linguistic form and meaning. However, if we look beyond the more familiar Indo-European languages and also include both spoken and signed language modalities, we find that motivated, iconic form-meaning mappings are, in fact, pervasive in language. In this paper, we review the different types of iconic mappings that characterize languages in both modalities, including the predominantly visually iconic mappings found in signed languages. Having shown that iconic mapping are present across languages, we then proceed to review evidence showing that language users (signers and speakers) exploit iconicity in language processing and language acquisition. While not discounting the presence and importance of arbitrariness in language, we put forward the idea that iconicity need also be recognized as a general property of language, which may serve the function of reducing the gap between linguistic form and conceptual representation to allow the language system to "hook up" to motor, perceptual, and affective experience.