Potentially recursive structures emerge quickly when a new language community forms.

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 systematically 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.

The communicative importance of agent-backgrounding: Evidence from homesign and Nicaraguan Sign Language.

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.

Lexical Iconicity is differentially favored under transmission in a new sign language: The effect of type of iconicity.

Observations that iconicity diminishes over time in sign languages pose a puzzle--why should something so evidently useful and functional decrease? Using an archival dataset of signs elicited over 15 years from 4 first-cohort and 4 third-cohort signers of an emerging sign language (Nicaraguan Sign Language), we investigated changes in pantomimic (body-to-body) and perceptual (body-to-object) iconicity. We make three key observations: (1) there is greater variability in the signs produced by the first cohort compared to the third; (2) while both types of iconicity are evident, pantomimic iconicity is more prevalent than perceptual iconicity for both groups; and (3) across cohorts, pantomimic elements are dropped to a greater proportion than perceptual elements. The higher rate of pantomimic iconicity in the first-cohort lexicon reflects the usefulness of body-as-body mapping in language creation. Yet, its greater vulnerability to change over transmission suggests that it is less favored by children's language acquisition processes.

Structural cues for symmetry, asymmetry, and non-symmetry in Central Taurus Sign Language.

We investigate how predicates expressing symmetry, asymmetry and non-symmetry are encoded in a newly emerging sign language, Central Taurus Sign Language (CTSL). We find that predicates involving symmetry (i.e., reciprocal and symmetrical actions) differ from those involving asymmetry (i.e., transitive) in their use of the morphological devices investigated here: body segmentation, mirror-image articulators and double perspective. Symmetrical predicates also differ from non-symmetrical ones (i.e., intransitive) in their use of mirror-image configuration. Furthermore, reciprocal actions are temporally sequenced within a linear structure, whereas symmetrical actions are not. Thus, our data reveal that CTSL expresses each type of action with a particular combination of linguistic devices to encode symmetry, asymmetry, and non-symmetry. Furthermore, differences in the use of these devices across age cohorts of CTSL suggest that some have become more conventionalized over time. The same semantic distinctions have been observed - though with different realization - in another emerging sign language, Nicaraguan Sign Language (NSL). This converging suggests that natural human language learning capacities include an expectation to distinguish symmetry, asymmetry and non-symmetry.

The emergence of the formal category "symmetry" in a new sign language.

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.

Handshape complexity as a precursor to phonology: Variation, Emergence, and Acquisition.

In this paper two dimensions of handshape complexity are analyzed as potential building blocks of phonological contrast-joint complexity and finger group complexity. We ask whether sign language patterns are elaborations of those seen in the gestures produced by hearing people without speech (pantomime) or a more radical re-organization of them. Data from adults and children are analyzed to address issues of cross-linguistic variation, emergence, and acquisition. Study 1 addresses these issues in adult signers and gesturers from the United States, Italy, China, and Nicaragua. Study 2 addresses these issues in child and adult groups (signers and gesturers) from the United States, Italy, and Nicaragua. We argue that handshape undergoes a fairly radical reorganization, including loss and reorganization of iconicity and feature redistribution, as phonologization takes place in both of these dimensions. Moreover, while the patterns investigated here are not evidence of duality of patterning, we conclude that they are indeed phonological, and that they appear earlier than related morphosyntactic patterns that use the same types of handshape.

Is it language (yet)? The allure of the gesture-language binary.

Goldin-Meadow & Brentari (G-M&B) challenge the traditional separation between gestural and categorical language by modality, but they retain a binary distinction. However, multiple dimensions, particularly discreteness and combinatoriality, better carve up the range of linguistic and nonlinguistic human communication. Investigating transformation over time along these dimensions will reveal how the nature of language reflects human minds, rather than the world to which language refers.

The emergence of temporal language in Nicaraguan Sign Language.

Understanding what uniquely human properties account for the creation and transmission of language has been a central goal of cognitive science. Recently, the study of emerging sign languages, such as Nicaraguan Sign Language (NSL), has offered the opportunity to better understand how languages are created and the roles of the individual learner and the community of users. Here, we examined the emergence of two types of temporal language in NSL, comparing the linguistic devices for conveying temporal information among three sequential age cohorts of signers. Experiment 1 showed that while all three cohorts of signers could communicate about linearly ordered discrete events, only the second and third generations of signers successfully communicated information about events with more complex temporal structure. Experiment 2 showed that signers could discriminate between the types of temporal events in a nonverbal task. Finally, Experiment 3 investigated the ordinal use of numbers (e.g., first, second) in NSL signers, indicating that one strategy younger signers might have for accurately describing events in time might be to use ordinal numbers to mark each event. While the capacity for representing temporal concepts appears to be present in the human mind from the onset of language creation, the linguistic devices to convey temporality do not appear immediately. Evidently, temporal language emerges over generations of language transmission, as a product of individual minds interacting within a community of users.

Referential shift in Nicaraguan Sign Language: a transition from lexical to spatial devices.

Even the simplest narratives combine multiple strands of information, integrating different characters and their actions by expressing multiple perspectives of events. We examined the emergence of referential shift devices, which indicate changes among these perspectives, in Nicaraguan Sign Language (NSL). Sign languages, like spoken languages, mark referential shift grammatically with a shift in deictic perspective. In addition, sign languages can mark the shift with a point or a movement of the body to a specified spatial location in the three-dimensional space in front of the signer, capitalizing on the spatial affordances of the manual modality. We asked whether the use of space to mark referential shift emerges early in a new sign language by comparing the first two age cohorts of deaf signers of NSL. Eight first-cohort signers and 10 second-cohort signers watched video vignettes and described them in NSL. Narratives were coded for lexical (use of words) and spatial (use of signing space) devices. Although the cohorts did not differ significantly in the number of perspectives represented, second-cohort signers used referential shift devices to explicitly mark a shift in perspective in more of their narratives. Furthermore, while there was no significant difference between cohorts in the use of non-spatial, lexical devices, there was a difference in spatial devices, with second-cohort signers using them in significantly more of their narratives. This suggests that spatial devices have only recently increased as systematic markers of referential shift. Spatial referential shift devices may have emerged more slowly because they depend on the establishment of fundamental spatial conventions in the language. While the modality of sign languages can ultimately engender the syntactic use of three-dimensional space, we propose that a language must first develop systematic spatial distinctions before harnessing space for grammatical functions.

Infant rule learning: advantage language, or advantage speech?

Infants appear to learn abstract rule-like regularities (e.g., la la da follows an AAB pattern) more easily from speech than from a variety of other auditory and visual stimuli (Marcus et al., 2007). We test if that facilitation reflects a specialization to learn from speech alone, or from modality-independent communicative stimuli more generally, by measuring 7.5-month-old infants' ability to learn abstract rules from sign language-like gestures. Whereas infants appear to easily learn many different rules from speech, we found that with sign-like stimuli, and under circumstances comparable to those of Marcus et al. (1999), hearing infants were able to learn an ABB rule, but not an AAB rule. This is consistent with results of studies that demonstrate lower levels of infant rule learning from a variety of other non-speech stimuli, and we discuss implications for accounts of speech-facilitation.

Numerosity and number signs in deaf Nicaraguan adults.

What abilities are entailed in being numerate? Certainly, one is the ability to hold the exact quantity of a set in mind, even as it changes, and even after its members can no longer be perceived. Is counting language necessary to track and reproduce exact quantities? Previous work with speakers of languages that lack number words involved participants only from non-numerate cultures. Deaf Nicaraguan adults all live in a richly numerate culture, but vary in counting ability, allowing us to experimentally differentiate the contribution of these two factors. Thirty deaf and 10 hearing participants performed 11 one-to-one matching and counting tasks. Results suggest that immersion in a numerate culture is not enough to make one fully numerate. A memorized sequence of number symbols is required, though even an unconventional, iconic system is sufficient. Additionally, we find that within a numerate culture, the ability to track precise quantities can be acquired in adulthood.

The Emergence of Two Functions for Spatial Devices in Nicaraguan Sign Language.

The emergence of a new sign language since the late 1970s in Nicaragua enables us to capture the effects of successive cohorts of learners on an emerging grammar and to observe how elements are reshaped from one form and function to another. Here we document the contrastive use of a device that has been found to be central to the grammars of sign languages: the spatial modulation of signs. In Nicaraguan Sign Language, this device has two primary functions: expressing the participants of events (that is, indicating who), and describing locations and orientations of referents (that is, indicating where). We ask whether the two uses reduce to a single construction type, or if the more abstract who construction derived from the more iconic and concrete where construction. We compare the first two successive cohorts of deaf signers to acquire the language in its first decade. We find that as learners created new constructions to meet the new functions, they did not simply apply an already developed form more broadly, nor did they develop the more abstract application from the more iconic one. Instead, the more abstract who construction appears to have conventionalized first. Thus, the forms either emerged independently, or split very early in the 1980s, before either had developed as a consistently applied form.

Evidence from an emerging sign language reveals that language supports spatial cognition.

Although spatial language and spatial cognition covary over development and across languages, determining the causal direction of this relationship presents a challenge. Here we show that mature human spatial cognition depends on the acquisition of specific aspects of spatial language. We tested two cohorts of deaf signers who acquired an emerging sign language in Nicaragua at the same age but during different time periods: the first cohort of signers acquired the language in its infancy, and 10 y later the second cohort of signers acquired the language in a more complex form. We found that the second-cohort signers, now in their 20s, used more consistent spatial language than the first-cohort signers, now in their 30s. Correspondingly, they outperformed the first cohort in spatially guided searches, both when they were disoriented and when an array was rotated. Consistent linguistic marking of left-right relations correlated with search performance under disorientation, whereas consistent marking of ground information correlated with search in rotated arrays. Human spatial cognition therefore is modulated by the acquisition of a rich language.

The effects of BOTOX injections on emotional experience.

Although it was proposed over a century ago that feedback from facial expressions influence emotional experience, tests of this hypothesis have been equivocal. Here we directly tested this facial feedback hypothesis (FFH) by comparing the impact on self-reported emotional experience of BOTOX injections (which paralyze muscles of facial expression) and a control Restylane injection (which is a cosmetic filler that does not affect facial muscles). When examined alone, BOTOX participants showed no pre- to posttreatment changes in emotional responses to our most positive and negative video clips. Between-groups comparisons, however, showed that relative to controls, BOTOX participants exhibited an overall significant decrease in the strength of emotional experience. This result was attributable to (a) a pre- versus postdecrease in responses to mildly positive clips in the BOTOX group and (b) an unexpected increase in responses to negative clips in the Restylane control group. These data suggest that feedback from facial expressions is not necessary for emotional experience, but may influence emotional experience in some circumstances. These findings point to specific directions for future work clarifying the expression-experience relationship.

Language promotes false-belief understanding: evidence from learners of a new sign language.

Developmental studies have identified a strong correlation in the timing of language development and false-belief understanding. However, the nature of this relationship remains unresolved. Does language promote false-belief understanding, or does it merely facilitate development that could occur independently, albeit on a delayed timescale? We examined language development and false-belief understanding in deaf learners of an emerging sign language in Nicaragua. The use of mental-state vocabulary and performance on a low-verbal false-belief task were assessed, over 2 years, in adult and adolescent users of Nicaraguan Sign Language. Results show that those adults who acquired a nascent form of the language during childhood produce few mental-state signs and fail to exhibit false-belief understanding. Furthermore, those whose language developed over the period of the study correspondingly developed in false-belief understanding. Thus, language learning, over and above social experience, drives the development of a mature theory of mind.

How Does Facial Feedback Modulate Emotional Experience?

Contracting muscles involved in facial expressions (e.g. smiling or frowning) can make emotions more intense, even when unaware one is modifying expression (e.g. Strack, Martin, & Stepper, 1988). However, it is unresolved whether and how inhibiting facial expressions might weaken emotional experience. In the present study, 142 participants watched positive and negative video clips while either inhibiting their facial expressions or not. When hypothesis awareness and effects of distraction were experimentally controlled, inhibiting facial expressions weakened some emotional experiences. These findings provide new insight into ways that inhibition of facial expression can affect emotional experience: the link is not dependent on experimental demand, lay theories about connections between expression and experience, or the distraction involved in inhibiting one's expressions.

Language emergence: clues from a new bedouin sign.

A sign language has emerged among three generations of deaf people and their families in a Bedouin community in the Negev desert. This newly reported case sheds light on the minimal environmental social factors required to generate a language.

Children creating core properties of language: evidence from an emerging sign language in Nicaragua.

A new sign language has been created by deaf Nicaraguans over the past 25 years, providing an opportunity to observe the inception of universal hallmarks of language. We found that in their initial creation of the language, children analyzed complex events into basic elements and sequenced these elements into hierarchically structured expressions according to principles not observed in gestures accompanying speech in the surrounding language. Successive cohorts of learners extended this procedure, transforming Nicaraguan signing from its early gestural form into a linguistic system. We propose that this early segmentation and recombination reflect mechanisms with which children learn, and thereby perpetuate, language. Thus, children naturally possess learning abilities capable of giving language its fundamental structure.