Studies of homesigns have shed light on the human capacity for language and on the challenging problem of language acquisition. The study of homesign has evolved from a perspective grounded in gesture studies and child development to include sign language linguistics and the role of homesigns in language emergence at the community level. One overarching finding is that homesigns more closely resemble sign languages used by linguistic communities than they resemble the gestures produced by hearing people along with spoken language. Homesigns may not exhibit all of the linguistic properties of community languages, but the properties they do exhibit are language properties, and for the people who use them, homesigns are their language. Further, the linguistic structures in homesigns are innovated by the deaf people who use them and are imperfectly learned by their hearing communication partners. I close with a call to action: We cannot celebrate discoveries about the mind made possible by studies of homesigns and emerging languages while ignoring the pervasiveness of language deprivation among deaf people, and the relative lack of deaf participation in science, even in studies of sign languages. While the scientific community learns much from studying homesigns and sign languages, we also have a responsibility to work toward ensuring that every deaf person has access to language, communication, and education.

One structural dimension that varies across languages is the simultaneous or sequential expression of meaning. Complex predicates can layer meanings together simultaneously in a single -verb predicate (SVP) or distribute them sequentially in a multiple -verb predicate (MVP). We ask whether typological variability in this dimension might be a consequence of systematic patterns of diachronic change. We examine the distribution of markers of agency and number within the verb phrase (the predicate) in the earliest stages of a young, emerging sign language in Nicaragua, Lengua de Se & ntilde;as Nicarag & uuml;ense (LSN), beginning with homesign systems like those from which LSN originated, and progressing through two decades of transmission to new learners. We find that: (i) LSN2 signers are more likely to produce MVPs than homesigners or LSN1 signers; (ii) in the MVPs they do produce, homesigners and LSN1 signers are more likely to produce predicates that mark both agency and number simultaneously on at least one of the verbs; LSN2 signers are just as likely to produce sequences with verbs that mark agency and number in sequentially separate verbs. We discuss how language acquisition, modality, and structure, as well as specific social factors associated with each of the groups, play a role in driving these changes, and how, over time, these patterns of change might yield the diversity of forms observed across spoken and signed languages today.

Human languages can express an infinite number of thoughts despite having a finite set of words and rules. This is due, in part, to recursive structures, which allow us to embed one instance of a rule inside another. We investigated the origins of recursion by studying the development of Nicaraguan Sign Language (LSN), which emerged in the last 40 years and is not derived from any existing language. Before this, deaf individuals in Nicaragua lacked access to language models and each individual created their own gestural system, called homesign. We tested four groups: homesigners, who represent the point of origin, and the first three generations of LSN signers, who represent consecutive stages in the language's development. We used a task that was designed to elicit sentences with relative clauses, a device that allows for the recursive embedding of sentences inside of sentences (e.g., [the girl [who was drawing] removed the picture]). Signers in all three LSN cohorts consistently produced utterances that appeared to have embedded predicates (girl draw remove picture) which served the function of a relative clause (picking out the correct member of a set, based on previously mentioned information). Furthermore, in these utterances, the first verb was shorter than the second and shorter than the same verb in parallel unembedded structures. In contrast, homesigners produced similar utterances in embedded and unembedded contexts. They did not reintroduce previously mentioned information or produce reduced verb forms in the embedded context. These results demonstrate that syntactic embedding that is potentially recursive can emerge very early in a language. These embedded predicates, however, may not be widespread, or sys-tematically marked, in homesign systems. This raises the possibility that the emergence of recursive linguistic structure is a consequence of interaction within a language community. These findings pave the way for future work which investigates the syntactic form of these embedded predicates and explores whether multiple levels of embedding are possible.

Research has shown a link between the acquisition of numerical concepts and language, but exactly how linguistic input matters for numerical development remains unclear. Here, we examine both symbolic (number word knowledge) and non-symbolic (numerical discrimination) numerical abilities in a population in which access to language is limited early in development—oral deaf and hard of hearing (DHH) preschoolers born to hearing parents who do not know a sign language. The oral DHH children demonstrated lower numerical discrimination skills, verbal number knowledge, conceptual understanding of the word “more”, and vocabulary relative to their hearing peers. Importantly, however, analyses revealed that group differences in the numerical tasks, but not vocabulary, disappeared when differences in the amount of time children had had auditory access to spoken language input via hearing technology were taken into account. Results offer insights regarding the role language plays in emerging number concepts. © 2023, The Author(s).

The ability to associate different types of number representations referring to the same quantity (symbolic Arabic numerals, signed/spoken number words, and nonsymbolic quantities), is an important predictor of overall mathematical success. This foundational skill-mapping-has not been examined in deaf and hard-of-hearing (DHH) children. To address this gap, we studied 188 4 1/2 to 9-year-old DHH and hearing children and systematically examined the relationship between their language experiences and mapping skills. We asked whether the timing of children's language exposure (early vs. later), the modality of their language (signed vs. spoken), and their rote counting abilities related to mapping performance. We found that language modality did not significantly relate to mapping performance, but timing of language exposure and counting skills did. These findings suggest that early access to language, whether spoken or signed, supports the development of age-typical mapping skills and that knowledge of number words is critical for this development.

Much research has found disrupted executive functioning (EF) in deaf and hard-of-hearing (DHH) children; while some theories emphasize the role of auditory deprivation, others posit delayed language experience as the primary cause. This study investigated the role of language and auditory experience in parent-reported EF for 123 preschool-aged children (M-age = 60.1 months, 53.7% female, 84.6% White). Comparisons between DHH and typically hearing children exposed to language from birth (spoken or signed) showed no significant differences in EF despite drastic differences in auditory input. Linear models demonstrated that earlier language exposure predicted better EF (beta = .061-.341), while earlier auditory exposure did not. Few participants exhibited clinically significant executive dysfunction. Results support theories positing that language, not auditory experience, scaffolds EF development.

While mathematics anxiety (MA) has been widely researched in recent decades, this study addresses significant gaps: namely, research that explores the relationship between MA and self-reported mathematics experiences; samples adults with a range of MA levels; and controls for general anxiety. Additionally, the study sampled deaf and hard of hearing (DHH) students, whose diverse life and educational experiences often differ from hearing students'. We investigated whether DHH students' experiences with mathematics (i.e., parental behaviors, school environment, and mathematics feelings) and demographic variables (i.e., hearing status, age, and gender) predict their MA, and whether these relationships differ from those in hearing students. Self-report questionnaires were completed by 296 DHH and hearing college students. Linear regression analyses controlling for general anxiety led to the following inference: DHH students who reported more positive attitudes toward mathematics and school environments demonstrated higher MA. Also, the relationships between mathematics feelings, parental behaviors, and MA differed between DHH and hearing students. Logistic regression analyses showed no contribution of MA to students' likelihood of pursuing STEM degrees in either DHH or between DHH and hearing groups. Overall, this work breaks new ground in the study of MA in DHH students and challenges standard views of the relationships between MA and individual experiences.

In this work, we address structural, iconic and social dimensions of the emergence of phonological systems in two emerging sign languages. A comparative analysis is conducted of data from a village sign language (Central Taurus Sign Language; CTSL) and a community sign language (Nicaraguan Sign Language; NSL). Both languages are approximately 50 years old, but the sizes and social structures of their respective communities are quite different. We find important differences between the two languages' handshape inventories. CTSL's handshape inventory has changed more slowly than NSL's across the same time period. In addition, while the inventories of the two languages are of similar size, handshape complexity is higher in NSL than in CTSL. This work provides an example of the unique and important perspective that emerging sign languages offer regarding longstanding questions about how phonological systems emerge.

Some concepts are more essential for human communication than others. In this paper, we investigate whether the concept of agent-backgrounding is sufficiently important for communication that linguistic structures for encoding this concept are present in young sign languages. Agent-backgrounding constructions serve to reduce the prominence of the agent - the English passive sentence a book was knocked over is an example. Although these constructions are widely attested cross-linguistically, there is little prior research on the emergence of such devices in new languages. Here we studied how agent-backgrounding constructions emerge in Nicaraguan Sign Language (NSL) and adult homesign systems. We found that NSL signers have innovated both lexical and morphological devices for expressing agent-backgrounding, indicating that conveying a flexible perspective on events has deep communicative value. At the same time, agent-backgrounding devices did not emerge at the same time as agentive devices. This result suggests that agent-backgrounding does not have the same core cognitive status as agency. The emergence of agent-backgrounding morphology appears to depend on receiving a linguistic system as input in which linguistic devices for expressing agency are already well-established.

Logical properties such as negation, implication, and symmetry, despite the fact that they are foundational and threaded through the vocabulary and syntax of known natural languages, pose a special problem for language learning. Their meanings are much harder to identify and isolate in the child's everyday interaction with referents in the world than concrete things (like spoons and horses) and happenings and acts (like running and jumping) that are much more easily identified, and thus more easily linked to their linguistic labels (spoon, horse, run, jump). Here we concentrate attention on the category of symmetry [a relation R is symmetrical if and only if (iff) for all x, y: if R(x,y), then R(y,x)], expressed in English by such terms as similar, marry, cousin, and near. After a brief introduction to how symmetry is expressed in English and other well-studied languages, we discuss the appearance and maturation of this category in Nicaraguan Sign Language (NSL). NSL is an emerging language used as the primary, daily means of communication among a population of deaf individuals who could not acquire the surrounding spoken language because they could not hear it, and who were not exposed to a preexisting sign language because there was none available in their community. Remarkably, these individuals treat symmetry, in both semantic and syntactic regards, much as do learners exposed to a previously established language. These findings point to deep human biases in the structures underpinning and constituting human language.