Abstract There would be little adaptive value in a complex communication system like human language if there were no ways to detect and correct problems. A systematic comparison of conversation in a broad sample of the world’s languages reveals a universal system for the real-time resolution of frequent breakdowns in communication. In a sample of 12 languages of 8 language families of varied typological profiles we find a system of ‘other-initiated repair’, where the recipient of an unclear message can signal trouble and the sender can repair the original message. We find that this system is frequently used (on average about once per 1.4 minutes in any language), and that it has detailed common properties, contrary to assumptions of radical cultural variation. Unrelated languages share the same three functionally distinct types of repair initiator for signalling problems and use them in the same kinds of contexts. People prefer to choose the type that is the most specific possible, a principle that minimizes cost both for the sender being asked to fix the problem and for the dyad as a social unit. Disruption to the conversation is kept to a minimum, with the two-utterance repair sequence being on average no longer that the single utterance which is being fixed. The findings, controlled for historical relationships, situation types and other dependencies, reveal the fundamentally cooperative nature of human communication and offer support for the pragmatic universals hypothesis: while languages may vary in the organization of grammar and meaning, key systems of language use may be largely similar across cultural groups. They also provide a fresh perspective on controversies about the core properties of language, by revealing a common infrastructure for social interaction which may be the universal bedrock upon which linguistic diversity rests.

Citation: Dingemanse M, Roberts SG, Baranova J, Blythe J, Drew P, Floyd S, et al. (2015) Universal Principles in the Repair of Communication Problems. PLoS ONE 10(9): e0136100. https://doi.org/10.1371/journal.pone.0136100 Editor: Sonja Kotz, Max Planck Institute for Human Cognitive and Brain Sciences, GERMANY Received: May 11, 2015; Accepted: July 29, 2015; Published: September 16, 2015 Copyright: © 2015 Dingemanse et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited Data Availability: All relevant data are within the paper and its Supporting Information files (S1–S6 Text, S1 Data). Funding: This research was supported by ERC projects HSSLU (240853, to NJE) and INTERACT (269484, to SCL) and by the Max Planck Gesellschaft. Competing interests: The authors have declared that no competing interests exist.

Introduction A design requirement for a communication system with complex, varying content, is that when communication fails there should be some mechanism to ‘repair’ it. This paper investigates a key system of communication repair found in the core ecological niche for language, conversation [1,2]. We compare conversation in 12 languages from 5 continents and find a robust system for the real-time resolution of breakdowns in communication. We find that this system of other-initiated repair is frequently used, that its basic structure is the same across languages, and that its principles of usage reveal the fundamentally cooperative nature of human communication. In other-initiated repair, a recipient of a linguistic message signals that there is a problem understanding or hearing what was said, and the sender then ‘fixes’ it. Aspects of this system have been described for English [3–10], but no broad-ranging, systematic cross-cultural comparison has been made. Comparative work is important for two reasons. First, methods for recovery from communication problems vary radically across species. Non-human animal communication systems feature re-doings, detection of unreliable signals, and failures of communication being allowed to stand or inferred later [11–14], but there appear to be few if any mechanisms for the interactive recognition and repair of breakdowns. If cross-cultural investigation revealed a basic set of mechanisms for interactive repair in human language, this would shed new light on human capacities for language, and provide a key point of comparison for the cross-species ethology of communication. A second reason for systematic comparison is the common assumption of cross-cultural variation within our species: “While clarification is a universal activity, the manner in which clarification is accomplished varies crossculturally” [15,16]. Different languages may offer different ways to solve communication problems; or there may be a common toolbox of techniques, with not all languages using all of the tools. Work in interactional linguistics has suggested that in the domain of self-initiated repair, interactional practices are constrained by the syntactic organisation of a language [17]; this raises the question to what extent strategies for other-initiated repair may be language-specific. Yet there are also arguments in favour of a universal system. While languages may vary in fundamental ways, from sound systems to syntax to semantics [18,19], recent work has shown robust universal features in the basic infrastructure for social interaction, for instance the turn-taking system [20,21]. Likewise, practices of other-initiated repair may be so crucial to the organisation of social interaction and the achievement of joint goals that there remains little room for radical cross-cultural variation [1,2,22,23]. As one account proposes, “It is hard to imagine a society or culture whose organization of repair does not include a repair component, and one that works more or less like the one I have sketched” [1]. This generates two opposing hypotheses: a pragmatic diversity hypothesis, by which systems of language use reflect cultural differences and therefore may vary across cultural groups (implying or at least allowing universality in other areas of language such as grammar); and a pragmatic universals hypothesis, by which systems of language use are largely similar across cultural groups (allowing diversity in other areas of language) [23]. Here we test these opposing hypotheses in the domain of other-initiated repair. We also test the cross-linguistic generality of two existing proposals about repair. The first is an ordering of repair initiation techniques from ‘weak’ to ‘strong’ [3], according to which participants prefer more specific repair initiation techniques like ‘Who?’ over less specific ones like ‘Huh?’ when they can: the ‘strongest initiator rule’ [24]. The second is a principle of least collaborative effort, according to which the selection of repair initiation techniques would be done in such a way that it minimizes joint work [24,25]. Both proposals have been put forward on the basis of English data; our cross-cultural study allows us to test whether they apply in conversation across languages.

Materials and Methods We built video corpora of maximally informal social interaction from 12 languages of 8 language families spoken on 5 continents (Table 1). The languages vary fundamentally in typological profile (e.g., sound structure, word order, and grammatical systems), semiotic modality (spoken as well as signed), and societal setting (from small-scale peasant societies to large-scale post-industrial nations). Data were collected from consenting participants in accordance with protocols approved by the ethical review board of the Seventh EU Framework (240853 HSSLU). Consent procedures were adapted to local requirements following recommended practices in anthropology and linguistics [26,27] in a procedure approved by the ethical review board: written consent for literate participants, and audio-recorded verbal consent for non-literate participants, all archived with the conversational data. Data collection was limited to spontaneous, naturally occurring conversations between families and friends, following established methods for the collection and sampling of conversational data [21,28]. Participants often engaged in additional activities during these conversations (e.g., eating, playing games, preparing food), introducing variation which we use as a lever to gauge how factors like attention influence the signalling and resolution of communicative trouble. PPT PowerPoint slide

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larger image TIFF original image Download: Table 1. Languages and researchers involved in this study. https://doi.org/10.1371/journal.pone.0136100.t001 Other-initiated repair is done in a question-and-answer type exchange that briefly disrupts the progress of an interaction. We focus on the following elements of this system and their relations to each other (Fig 1): repair initiator, a signal from speaker B of a problem with what speaker A just said, which A should fix; repair solution, how the problem is fixed, e.g., by A repeating the trouble source turn or part of it, by specifying something that was vague or missing, or by confirming that a solution proposed by B was the right one; and repair sequence, a side sequence [4] consisting of repair initiator and solution taken together. Throughout, B refers to the person initiating repair and A to the original speaker and provider of the repair solution. PPT PowerPoint slide

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larger image TIFF original image Download: Fig 1. Elements of other-initiated repair. Repair sequences consist of a repair initiator that points back to a prior turn (trouble source) and points forward to a next turn (repair solution) [3]. https://doi.org/10.1371/journal.pone.0136100.g001 We systematically sampled the conversations for occurrences of other-initiated repair, taking 10-minute segments from as many different interactions as possible to ensure against any bias from over-representation of particular interactions or speakers. Based on close analysis of other-initiated repair sequences, a cross-linguistic coding scheme was developed and applied [29,30]. The coding scheme captured facts about linguistic resources (e.g., interjections, question markers, repetition, confirmation), conversational sequence (e.g., whether the repair initiation was the first or a subsequent attempt at resolving the trouble, whether the turn preceding the repair initiation was a question or an answer), and environmental and attentional factors (e.g., whether there was auditory or visual interference, whether B was involved in a parallel activity). To maximise coding consistency across the individual languages, all researchers participated in the development of the coding scheme and in the calibration of joint understanding of the coding categories. We checked coding reliability for all coders based on a common English dataset. For the quantitative analyses, we consider only variables that achieved a Krippendorff’s α [31] of ≥ 0.66 or ≥ 75% agreement (we use % agreement for variables that achieved low α values due to skewed distributions, the well-known ‘high agreement, low consistency’ paradox [32,33]). Two variables were recoded using a narrower coding instruction. In addition to the coded variables, our quantitative analyses use 13 automatically calculated measures like absolute and relative length of elements of the repair sequence, Levenshtein distances, source recording, language, language family, etc. (as detailed in S2 Text). Data were analysed using linear mixed effects models [34] for maximal statistical power, while controlling for historical relations between languages (Galton’s problem [35]) and other dependencies and imbalances in the data. Examples of basic repair initiator types in all the languages are given in S1 Text. Details about data structure and models are provided in S2–S6 Texts. Reported statistics come from mixed effects model estimates unless otherwise noted.

Discussion Our findings offer support for the pragmatic universals hypothesis: while languages may vary in the organization of grammar and meaning, key systems of language use may be largely similar across cultural groups. The pragmatic universals we have found reveal remarkable unity where prior work proposed cultural diversity, and provide robust cross-cultural support for proposals hitherto founded only on English data [3,24]. In particular, our results provide a strong empirical verification of the cross-cultural relevance of the strongest initiator rule and the principle of least collaborative effort in conversation [24,50]. The sheer frequency of other-initiated repair (about once every 1.4 minutes across all the languages) brings home the fundamental importance of this system to human communication. The properties of the system (with three basic types accounting for the vast majority of repair initiations across languages) uncover linguistic universals of a kind not described before. The three principles of specificity, conservation, and division of labour reveal a common element of prosociality underlying the operation of the repair system in all of the languages. Although methods to recover from breakdowns may seem essential to any communication system, things could have been otherwise. In many animal communication systems, robustness in the face of signal unreliability is provided by such properties as redundancy, multi-modality, repetition, and exaggerated or costly signals [52,53,13], all features also found in human language. Yet no other animal communication system appears to offer the kind of mechanisms for the interactive resolution of trouble we find in other-initiated repair. Our finding that it is a core feature of all 12 languages in our sample thus constitutes a substantial universal of human language, and points to the uniquely human sociality that underlies it. Another sense in which things could have been otherwise is in the distribution and use of strategies for the other-initiation of repair. It is conceivable that there are languages in which speakers use a form like ‘Huh?’ exclusively, eschewing more specific alternatives, perhaps similar to the situation in which some languages lack counting words beyond ‘one’, ‘two’, and ‘many’ [54]. Yet we haven’t found such a language; we find instead that the three basic types—open request, restricted request, and restricted offer—are used in the same situations across all the languages in our sample, showing remarkable convergence in systems of language usage and again pointing to the cooperative properties of human communication. Our findings are based on conversation, the core ecological niche for language. As such, they provide a baseline for future work on the specifics of the repair system in different settings and societies. Corpus-based studies can build on them to investigate how different communicative settings may deploy variations of the basic system [55,56], and studies of language development can examine how and in which order children across cultures master the basic types of repair initiators [57,58]. The findings also provide an impetus for experimental work on the social and contextual factors involved in repair [59,60], and for modelling work on the theoretical aspects of achieving mutual understanding [61,62]. Finally, they provide a point of reference for cross-species ethological studies of mechanisms for repairing communicative breakdowns. Language is a form of animal behaviour, and so, one might argue, it should be studied using the tried and tested methods of ethology [63–65]: starting with the systematic field observation of natural behaviour to establish the facts, then moving to well-designed experiments, and iterating this process to refine models and theories. Curiously, over the last 50 years, observations of natural behaviour have played little role in the discipline of linguistics, due in large part to an overly narrow conception of language as the mental competence for generating sentences [66,67]. Here we have shown that the systematic observation of language usage reveals complex phenomena such as repair that are clearly fundamental to human language, and that are tied to our uniquely human sociality. The system for other-initiated repair described here is particularly significant for showcasing three core elements essential to human language. The first element is the property of self-referentiality (or reflexivity) in signalling: the possibility of a communication system being used not only for communicating about objects and entities in the physical world, but also for communicating about itself. Repair initiators like Huh?, What did you say?, Who?, You mean John?, as well as those repeating all or part of the prior turn, are specifically designed for drawing attention to particular elements of the communication system as it is used. Self-referentiality is a hallmark of human language [68–70], and its concrete and common use in other-initiated repair may well provide one of the main drivers behind its adaptive value in natural language. The second element is our species’ possession of a full-blown theory of mind [71,72]: a degree of social intelligence that allows and motivates individuals to finely monitor discrepancies in states of knowledge and understanding between self and others. Conversational repair is one of the places where speakers’ theories of mind come to the surface [73], and the mechanisms of other-initiated repair offer a universally shared set of tools for the interactive achievement of mutual understanding. Third is our species’ unique capacity for cooperative and collaborative action [74,75], whereby two or more individuals can jointly commit to a shared course of behaviour, being thereby morally accountable for the success of that course of behaviour. We see these prosocial motives in action in the sequences of other-initiated repair, insofar as these sequences would not be possible without (i) fully-fledged cooperation, (ii) a willingness to delay current line of joint action and assist the other party, and (iii) a capacity to suspend and then resume the current line of action (which requires inhibiting current goals and stacking reasons for action). The cross-culturally common properties of other-initiated repair make it one of the most vivid demonstrations of the ultrasocial nature of humans [76,77].

Conclusions We have shown strong and systematic similarities in the properties and principles of use of a system for other-initiated repair in a diverse sample of languages, controlling for situation types, historical relationships and a range of other variables. While linguistic details of repair initiators can vary from language to language, both the general shape of the system and its principles of use in informal conversation are strongly similar across different languages, suggesting that we are tapping into the very infrastructure for social interaction [2]. These findings direct our attention to the fundamentally social nature of language. Contrary to common expectations in theoretical linguistics about the chaotic and degenerate nature of language usage [66,67], we find strong regularity and normativity in conversation, down to the level of how problems are signalled and solved. The possibility of a universal system for other-initiated repair is important for current controversies about the essence of human language [78–80]. While those debates have focused on word- and sentence-level features like sound systems and grammatical structures, here we propose language universals in the patterns of conversation. This presents an opportunity for progress in answering the question: If language is universally and quintessentially human, what is at its core? The repair system we observe is one of the crucial safeguarding mechanisms for coherence in social interaction. It exhibits and exploits three elements that are crucial to human language and arguably unique to our species: self-referentiality, social intelligence, and collaborative action. If there is a universal core to language, these are the kinds of things it is made of.

Author Contributions Conceived and designed the experiments: MD J. Baranova J. Blythe PD SF RSG KHK SCL EM GR NJE. Performed the experiments: MD J. Baranova J. Blythe SF RSG KHK SCL EM GR NJE. Contributed reagents/materials/analysis tools: SGR MD J. Baranova J. Blythe PD SF. Wrote the paper: MD NJE SGR SCL. Carried out field work, corpus collection, transcription, translation, and data collection: MD J. Baranova J. Blythe SF RSG KHK SCL EM GR NJE; Participated in primary data analysis and formulation of design of the coding: MD J. Baranova J. Blythe PD SF RSG KHK SCL EM GR NJE; Designed and wrote the coding scheme: MD KHK NJE; Oversaw coding reliability: MD KHK; Oversaw data collection and did data analysis: MD; Did mixed effects modeling and statistics: SGR; Coordinated the project: MD NJE.