We used agent-based modelling to study the emergence of linguistic conventions for basic word order (the order of subject, object and verb) in different populations. As a starting point, we take word order variation based on semantic properties, as observed in improvised gesture experiments. In our first simulation we explore the relative contributions of two pressures, one for semantically conditioned variation, and the other structural priming (which takes place when two individuals engage in communication), and show that a relatively increasing influence of structural priming best explains an increase in word order regularity. Next we implement a larger simulation, investigating how properties of the population affect regularization of word order. Our models compare population sizes with different population densities, and show that the speed of regularization in languages is heavily influenced by population density, and population size has little effect.

What drives lexical alignment in the context of language emergence? We test the theory that limited context promotes alignment, because individuals cannot make use of iconic mappings between shared meanings and forms. Using a novel referential communication paradigm where participants use pre-recorded gesture videos to communicate, we test different context conditions. We find, unexpectedly, no alignment differences between dyads with shared context and dyads with limited context, even though the former have fewer communicative errors. Importantly, we do observe differences when it comes to the iconic strategies used: less shared context promotes the use of (shared) visual iconicity.

In this paper we investigate a hypothesized cognitive bias forisomorphic mappings between conceptual structure and linearorder in the noun phrase. This bias has been proposed as a pos-sible explanation for a striking asymmetry in the typology ofthe noun phrase–linear orders which place the adjective clos-est to the noun, then the numeral, then the demonstrative, areover-represented in the world’s languages. Previous experi-mental work has provided evidence that an isomorphism biasaffects English-speaking learners’ inferences about the relativeorder of modifiers in an artificial language. Here, we use thesilent gesture paradigm to explore whether the isomorphismbias influences spontaneous gestures innovated by participantsin a modality with which they have relatively little prior experi-ence. We find that gesture string order largely conforms to thesame striking pattern found in noun phrase typology, support-ing the role of the isomorphism bias in shaping the emergenceof language (and language-like) systems.

Studying the silent gesture of hearing non-signers is a crucial tool for shedding light on natural language phenomena.Previous studies have found that properties of the meanings conveyed in silent gesture can influence word order. Forinstance, participants prefer SOV ordering for extensional events (man carries ball), while for intensional events (in whichthe object is possibly non-existent or dependent on the action; e.g., man thinks of guitar, woman builds house) there isa cross-linguistic preference for SVO (Schouwstra & de Swart, 2014). Eliciting descriptions of the two event types inNicaraguan Sign Language, we found evidence for these lab-documented word order preferences in an emergent naturallanguage: objects precede verbs for extensional events, but follow verbs for intensional events. However, this wordorder pattern is manifested differently in Nicaraguan Sign (the result only surfaced in a sub-string analysis), because thepreference interacts with NSLs language-internal constraint for verb-finalness.

Typological analysis of the world’s language shows that, of the 6 possible basic word orders, SOV and SVO orders are predominant, a preference supported by experimental studies in which participants improvise gestures to describe events. Silent gesture studies have also provided evidence for natural ordering patterns, where SOV and SVO orders are used selectively depending on the semantics of the event, a finding recently supported by data from natural sign languages. We present an artificial language learning task using gesture to ask to what extent preferences for natural ordering patterns, in addition to biases for regular languages, are at play during learning in the manual modality.

For a gesture to be successful, observers must recognize its communicative purpose. Are communicators sensitive to this problem and do they try to ease their observer’s inferential burden? We propose that people shape their gestures to help observers easily infer that their movements are meant to communicate. Using computational models of recursive goal inference, we show that this hypothesis predicts that gestures ought to reveal that the movement is inconsistent with the space of non-communicative goals in the environment. In two gesture-design experiments, we find that people spontaneously shape communicative movements in response to the distribution of potential instrumental goals, ensuring that the movement can be easily differentiated from instrumental action. Our results show that people are sensitive to the inferential demands that observers face. As a result, people actively work to help ensure that the goal of their communicative movement is understood.

Though most documented sign languages make use of spaceto denote relationships between predicate arguments, studiesof emerging sign languages suggest that spatial reference doesnot emerge fully-formed but takes time to develop. We presentan artificial sign language learning experiment that expandsthe cultural evolutionary framework to investigate complexlinguistic constructions. Our results demonstrate the gradualemergence of consistent devices to distinguish between sen-tence arguments, some of which rely on iconic spatial con-trasts. These findings mirror data from emerging sign lan-guages and point to the cultural mechanisms that facilitate theevolution of complex linguistic structures.

While the grammatical use of space for referential strategies is attested across many sign languages of Western Europe, Kata Kolok, a rural sign language used in Northern Bali, has not developed anaphoric pointing in space nor agreement verbs (Engberg-Pedersen, 1993; Liddell, 2003; de Vos, 2012). To find out whether such typological differences can be explained by differences in the respective co-speech gesture systems, this preregistered study is collecting data for a cross-cultural comparison. Building on Motamedi et al. (2021), we are conducting studies in Bali and the Netherlands using an iterated learning silent gesture paradigm in which hearing people communicate transitive events using only gestures. Preliminary data indeed suggest that our Balinese participants do not employ space the same way our Dutch participants do. We will present comparative analyses and evaluate the role of co-speech gesture systems in sign language emergence in the lab or when evolving from spontaneous interaction.

Emblems (also called conventional gestures) are a powerful, yet often overlooked part of humans' communicative tool-kit. These gestures rapidly express encapsulated messages, such as waving a hand to greet someone and shoulder shrugging to reveal a lack of knowledge. We hypothesized that emblems are shaped by a universal pressure to reveal their communicative purpose, and they should therefore be unconfounded with movement typically produced to accomplish non-communicative goals. We present evidence for this hypothesis using a novel dataset of over 250 emblems from around the world: Over 95% of these gestures have forms that support observers' inferences, suggesting that emblems are shaped to ease observers' inferential burden. Finally, in a gesture-creation experiment, we show that these inference-guiding features emerge spontaneously without the need for observer feedback or cultural transmission. Taken together, these complementary approaches provide insight into how goal inferential processes may explain the shape of communicative actions across cultures.