Volume 9, Issue s1 - Special Issue: Measuring Language Complexity; Editors: Katharina Ehret, Aleksandrs Berdicevskis, Christian Bentz, and Alice Blumenthal-Dramé

This special issue focuses on measuring language complexity. The contributions address methodological challenges, discuss implications for theoretical research, and use complexity measurements for testing theoretical claims. In this introductory article, we explain what knowledge can be gained from quantifying complexity. We then describe a workshop and a shared task which were our attempt to develop a systematic approach to the challenge of finding appropriate and valid measures, and which inspired this special issue. We summarize the contributions focusing on the findings which can be related to the most prominent debates in linguistic complexity research.

In linguistics, there is little consensus on how to define, measure, and compare complexity across languages. We propose to take the diversity of viewpoints as a given, and to capture the complexity of a language by a vector of measurements, rather than a single value. We then assess the statistical support for two controversial hypotheses: the trade-off hypothesis and the equi-complexity hypothesis. We furnish meta-analyses of 28 complexity metrics applied to texts written in overall 80 typologically diverse languages. The trade-off hypothesis is partially supported, in the sense that around one third of the significant correlations between measures are negative. The equi-complexity hypothesis, on the other hand, is largely confirmed. While we find evidence for complexity differences in the domains of morphology and syntax, the overall complexity vectors of languages turn out virtually indistinguishable.

We present an analysis of eight measures used for quantifying morphological complexity of natural languages. The measures we study are corpus-based measures of morphological complexity with varying requirements for corpus annotation. We present similarities and differences between these measures visually and through correlation analyses, as well as their relation to the relevant typological variables. Our analysis focuses on whether these ‘measures’ are measures of the same underlying variable, or whether they measure more than one dimension of morphological complexity. Principal component analysis indicates that the first principal component explains 92.62 percent of the variation in eight measures, indicating a strong linear dependence between the complexity measures studied.

The interaction of morphosyntactic features has been of great interest in research on linguistic complexity. In this paper we approach such interactions in possessive noun phrases. First, we study the interaction of head marking and dependent marking in this domain with typological feature data and with multilingual corpus data. The data suggest that there is a clear inverse relationship between head and dependent marking in possessive noun phrases in terms of complexity. The result points to evidence on complexity trade-offs and to productive integration of typological and corpus-based approaches. Second, we explore whether zero versus overt morphological marking as a measure of morphological complexity affects dependency length as a measure of syntactic complexity. Data from multilingual corpora suggest that there is no cross-linguistic trend between these measures in possessive noun phrases.

This paper investigates linguistic complexity across natural languages from a corpus-based perspective and relies on the assumptions of linguistic profiling as a methodological framework. We focus in particular on the domain of syntactic complexity and analyze the distribution of a set of features taken as proxies of complexity phenomena at sentence level, which were extracted from 63 treebanks annotated according to the Universal Dependencies formalism. This dataset guarantees that the features considered are modeling the same linguistic phenomena in different treebanks, allowing reliable comparison among languages. We show that our approach is able to identify tendencies of structural proximity between languages not necessarily in line with typologically-supported classification, thus shedding light on new corpus-based findings.

In this paper, I introduce a situational approach to the study of linguistic complexity. As opposed to most research on linguistic complexity, which has focused on the grammatical complexity of languages, I consider this topic from a situational perspective. I make two proposals. First, I claim that languages can vary in their situational diversity. Languages that have been adapted for a wider range of communicative contexts are more situationally complex than languages that have been adapted for a narrower range of communicative contexts. To support this claim, I consider examples of situational diversity from across a range of different languages and varieties of languages, drawing on empirical research from linguistics and anthropology. Second, I claim that situational diversity can help explain variation in grammatical complexity. I propose that increasing situational diversity in a language over time should lead to decreasing grammatical complexity. Furthermore, I argue that this trade-off between situational and grammatical complexity could explain how overall linguistic complexity could be maintained across languages and over time.

Since the 1990s linguistic complexity has become an important issue in second language acquisition (SLA) research and teaching: second language (L2) learners want to know how well they are progressing, while teachers and researchers are interested to find out which grade of complexity can be associated with a particular proficiency level. After a short sketch of the background to the construct of complexity, the paper presents an overview of how complexity is measured in SLA, how it is related to other constructs of language proficiency (in particular accuracy and fluency), and by which factors complexity may be affected: these concern both internal linguistic factors and external factors, like task-related features and type of instruction. The paper concludes with directions for future research, focusing on the need for non-redundant, valid and reliable measures, more developmental measures, a broader scope of complexity, combined cross-linguistic and longitudinal research, and more research in instructional practice.

Syntagmatic redundancy involves constructions in which a single meaning relates to more than one form in a clause or phrase. Redundancy has been claimed to facilitate language processing and acquisition, and to be a linguistic universal, because of these advantages. At the same time, the repeated expression of meaning has been argued to make languages more complex because of the violation of principles of economy and transparency. This paper first investigates the relation between redundancy and complexity by examining how redundancy scores on well-known metrics of complexity. This assessment shows that redundancy makes languages more complex according to metrics of objective complexity, while it has contradictory effects according to metrics of subjective complexity. To empirically test whether redundancy makes acquisition and processing easier or harder, a cross-linguistically valid way of measuring redundancy first needs to be established. The second part of the paper involves an attempt in this direction. It presents a typological study on cross-linguistic variation in four types of concord, showing that languages differ with respect to the number and types of redundancy constructions they allow. The ranking of the 50 sample languages as to their redundancy-based complexity serves as a testable hypothesis for acquisition and processing research.

Previous work has proposed that crosslinguistic ordering preferences are driven by several competing and cooperating factors simultaneously. Nevertheless, this proposal still lacks proper quantitative support, as most prior studies have focused on: (1) a limited set of factors and languages; (2) syntactic constructions that are not directly comparable or do not necessarily have flexible orderings. This study aims to bridge this gap, using the adpositional phrase (PP) typology as the test case. We focused on verb phrases in which the head verb has two PP dependents occurring on the same side ( He talked [ PP 1 with friends ] [ PP 2 for a long time ]), the order of which allows flexibility in at least some contexts. With multilingual corpora for 20 languages and computational techniques, we investigated the roles of four theoretically motivated constraints: dependency length, semantic closeness, lexical frequency and contextual predictability, the latter three of which have rarely been addressed systematically in a crosslinguistic context. Overall, dependency length is the strongest predictor and it is more effective in postverbal than preverbal domains. In certain preverbal cases where dependency length is not effective, semantic closeness and lexical frequency play a weak role. By contrast, contextual predictability does not seem to have a consistent effect across languages.

Sign languages are human communication systems that are equivalent to spoken language in their capacity for information transfer, but which use a dynamic visual signal for communication. Thus, linguistic metrics of complexity, which are typically developed for linear, symbolic linguistic representation (such as written forms of spoken languages) do not translate easily into sign language analysis. A comparison of physical signal metrics, on the other hand, is complicated by the higher dimensionality (spatial and temporal) of the sign language signal as compared to a speech signal (solely temporal). Here, we review a variety of approaches to operationalizing sign language complexity based on linguistic and physical data, and identify the approaches that allow for high fidelity modeling of the data in the visual domain, while capturing linguistically-relevant features of the sign language signal.

This article presents the results of a quantitative study in which the complexity levels of dialectal varieties belonging to the South Slavic dialect continuum are measured and analyzed. The sample comprises 919 data points, pertaining to the Bulgarian–Macedonian and Serbo-Croatian dialect continua. Complexity is viewed in this study as a property demonstrating variation across areas and subject to diachronic change which can be associated either with language-internal processes or with language contact. This study discusses which linguistic processes produced varying levels of complexity in the modern South Slavic varieties. In particular, a correlation of complexity with altitude and distance to the Albanian border, two factors which can be associated with degree of isolation versus contact of speech communities, is investigated for a subset of varieties spoken across the areas with bi- and multilingual population. Suggestions on which constellations of societal features could act as determinants of linguistic change are made for several areas within the South Slavic continuum. Particular attention is paid to the contact-related developments in the South Slavic varieties spoken in the areas of intensive past and present contact, such as the west of North Macedonia, the south of Montenegro, Kosovo, and Southeast Serbia.

Nouns and verbs are known to differ in the types of grammatical information they encode. What is less well known is the relationship between verbal and nominal coding within and across languages. The equi-complexity hypothesis holds that all languages are equally complex overall, which entails trade-offs between coding in different domains. From a diachronic point of view, this hypothesis implies that the loss and gain of coding in different domains can be expected to balance each other out. In this study, we test to what extent such inverse coevolution can be observed in a sample of 244 languages, using data from a comprehensive cross-linguistic database (Grambank) and applying computational phylogenetic modelling to control for genealogical relatedness. We find evidence for coevolutionary relationships between specific features within nominal and verbal domains on a global scale, but not for overall degrees of grammatical coding between languages. Instead, these amounts of nominal and verbal coding are positively correlated in Sino-Tibetan languages and inversely correlated in Indo-European languages. Our findings indicate that accretion and loss of grammatical information in nominal words and verbs are lineage-specific.