From spider dances to human language, multimodality is ubiquitous in natural communication systems. Much scholarship has been devoted to investigating why multimodality evolved and the role it plays in communication. Here, we highlight the role of multimodality in safeguarding the most fundamental prerequisite of all functioning, extant communication systems: honesty. We begin by introducing the arms race between honesty and deception in natural communication systems, and the critical role socially-mediated controls can play in maintaining signal honesty when classic, intrinsic costs are not sufficient. We next introduce three ways by which multimodality buffers signal honesty by 1) providing insurance against signal unreliability in dynamic environments, 2) forming an honest, multimodal gestalt with which to cross-validate signal honesty, and 3) increasing signal complexity, making the entire signal harder to fake. We then discuss the case of highly cooperative societies, with human language emphasized, and argue that signal honesty is important especially in complex and cooperative societies wherein the need to cooperate and be accepted as part of the group may supersede honesty. Finally, we propose future directions wherein human and non-human communication research could expand beyond the well trodden realms of competition and mate attraction to investigate the role of multimodality and honesty in cooperative, “cheap” signals, and emphasize the importance of drawing from both the human and non-human literatures in investigating the forces that have shaped the evolution of communication.

Social salience, the association of a social category with linguistic variables, has been hypothesized to be an important driver of language change. This hypothesis has not been rigorously tested due to the lack of a reliable measure of social salience. In this paper, we present Salience Categorization Test (Sali-CAT), a new approach to measuring the association of word variants with social categories across multiple lexical variables. The approach includes a customized experimental paradigm (three alternative forced choice) and a statistical method to establish the baseline Salience Ratio (Sali-RAT) score for word variants that do not have a bias in usage with respect to the social categories. We demonstrate the approach by testing the association of multiple variables with different generations of speakers in the Gurindji speech community.

As linguists theorize about language endangerment and loss (LEL), we must understand the big picture: the coexistence of languages in particular polities and how the competition that sometimes arises is resolved. Many concerns have been voiced about LEL since the early 1990s, but theoretical developments regarding language vitality lag far behind linguists’ current investment in language advocacy. While discussing issues such as the failure to connect the subject matter to language evolution in general, the framing of LEL as deleterious almost exclusively to ‘indigenous peoples’, a lack of historical time depth, and the omission of the ecological factors in typical approaches to LEL, I argue that linguistics should theorize about language vitality more adequately than has been the case to date.

In a number of signed languages, the distinction between nouns and verbs is evident in the morphophonology of the signs themselves. Here we use a novel elicitation paradigm to investigate the systematicity, emergence, and development of the noun-verb distinction (qua objects vs. actions) in an established sign language, American Sign Language (ASL), an emerging sign language, Nicaraguan Sign Language (NSL), and in the precursor to NSL, Nicaraguan homesigns. We show that a distinction between nouns and verbs is marked (by utterance position and movement size) and thus present in all groups—even homesigners, who have invented their systems without a conventional language model. However, there is also evidence of emerging crosslinguistic variation in whether a base hand is used to mark the noun-verb contrast. Finally, variation in how movement repetition and base hand are used across Nicaraguan groups offers insight into the pressures that influence the development of a linguistic system. Specifically, early signers of NSL use movement repetition and base hand in ways similar to homesigners but different from signers who entered the NSL community more recently, suggesting that intergenerational transmission to new learners (not just sharing a language with a community) plays a key role in the development of these devices. These results bear not only on the importance of the noun-verb distinction in human communication, but also on how this distinction emerges and develops in a new (sign) language.

We argue for an extension of the proposal that grammars are in part shaped by processing systems. Hawkins (2014) and others who have advanced this idea focus primarily on parsing. Our extension focuses on production, and we use that to explore explanations for certain subject/object asymmetries in extraction structures. The phenomenon we examine, which we term the mirror asymmetry, runs in opposite directions for within-clause and across-clause (long-distance) extraction, showing a preference for subject extraction in the former and for object extraction in the latter. We review several types of evidence suggesting that the mirror asymmetry and related phenomena are best explained by an account of the formation of grammars that assigns an important role to properties of sentence planning in production.

Recent research has revealed several languages (e.g. Chintang, Rarámuri, Tagalog, Murrinhpatha) that challenge the general expectation of strict sequential ordering in morphological structure. However, it has remained unclear whether these languages exhibit random placement of affixes or whether there are some underlying probabilistic principles that predict their placement. Here we address this question for verbal agreement markers and hypothesize a probabilistic universal of CATEGORY CLUSTERING, with two effects: (i) markers in paradigmatic opposition tend to be placed in the same morphological position (‘paradigmatic alignment’; Crysmann & Bonami 2016); (ii) morphological positions tend to be categorically uniform (‘featural coherence’; Stump 2001). We first show in a corpus study that category clustering drives the distribution of agreement prefixes in speakers' production of Chintang, a language where prefix placement is not constrained by any categorical rules of sequential ordering. We then show in a typological study that the same principle also shapes the evolution of morphological structure: although exceptions are attested, paradigms are much more likely to obey rather than to violate the principle. Category clustering is therefore a good candidate for a universal force shaping the structure and use of language, potentially due to benefits in processing and learning.

Variation is present in every language at every structural level. Though extremely complex, linguistic variation is not fully unpredictable. Previous research suggests that cognitive biases in learning favour conditioned variation: learners often make languages more predictable by eliminating variation or by conditioning it on context, pointing to the presence of biases against random variation. Learning biases favour lexical conditioning over more general category-based conditioning, though both occur in natural languages. Interaction may also contribute to shaping conditioned variation by providing a mechanism for interlocutors to develop a shared system through the coordination of individual preferences. In the present study, we investigated the role of dyadic interaction in the emergence of conditioned variation. We trained participants on an artificial language with unpredictable variation in plural marking and objects representing one or two semantic categories and had them play a communication game using the newly learned language. We hypothesised that interaction would introduce category-based conditioning, this being the simplest conditioned system in the language. Contrary to our expectations, we found no evidence of spontaneous category-based conditioning: participants either removed variation or conditioned marker use on lexical items. Further experiments are needed to explain the emergence of this common linguistic pattern.

We investigated how the presence of linguistic labels, their iconicity and mode of presentation (cued vs not cued) affect non-linguistic cognitive processing, focussing on the learning and visual discrimination of new categories. Novel species of aliens that mimicked natural categories were paired with iconic labels, non-iconic labels or no labels across two tasks. In the Training task participants learnt to categorise the aliens, with results showing that both labels and iconicity improved categorisation. We then used a Match to Sample task to test how these variables affect rapid visual discrimination. Results showed that the presence of labels, their iconicity and label cueing all lead to more rapid and accurate visual discrimination of newly acquired categories. We argue that this is due to iconicity exaggerating sensory expectations provided by linguistic labels, made more readily accessible by cueing. We also examine the possible implications of our results for the discussion about language evolution.

Our study explores aspects of human conversation within the framework of evolutionary psychology, focusing on the proportion of ‘social’ to ‘non-social’ content in casual conversation. Building upon the seminal study by Dunbar et al. (1997, Human Nature, 8, 231–246), which posited that two-thirds of conversation gravitates around social matters, our findings indicate an even larger portion, approximately 85% being of a social nature. Additionally, we provide a nuanced categorisation of ‘social’ rooted in the principles of evolutionary psychology. Similarly to Dunbar et al.’s findings, our results support theories of human evolution that highlight the importance of social interactions and information exchange and the importance of the exchange of social information in human interactions across various contexts.