Linguistic Complexity

Linguistic complexity (or: language complexity, complexity in language) is a multifaceted and multidimensional research area that has been booming since the early 2000s. The currently dominant research strand, which takes center stage in the present article, is concerned with structural complexity of entire languages, dialects, and varieties as such (so-called global linguistic complexity) or individual subsystems thereof (local linguistic complexity, as in phonology, inflectional morphology, syntax). In the context of these research lines the issue of how to measure structural complexity has come to play a prominent role, as only consistently applied complexity metrics, both from a purely system- (or langue-) perspective and from a usage- (or parole-/performance-) perspective, allow typological or cross-varietal comparisons. This comparative dimension was indeed the trigger of the renewed interest in linguistic complexity and complexity metrics when in 2001 a heated debate was launched challenging the so-called equi-complexity dogma (or: axiom). Following up on Sapir’s vivid analogy that “both simple and complex types of language of an indefinite number of varieties may be found spoken at any desired level of cultural advance” and thus “when it comes to linguistic form, Plato walks with the Macedonian swineherd, Confucius with the head-hunting savage of Assam” (see Sapir 1921, cited under Equi-Complexity Debate), this dogma had been entertained throughout most of the second half of the twentieth century and postulated that, structurally speaking, the grammars (i.e., morphology and syntax) of all languages are, on balance, equally complex. The basic idea behind this assumption, which is all it really was (as it had originally been formulated without any systematic comparison or quantitative backing), was that in a comparison of any two languages higher and lower degrees of complexity in different sub-domains of morphological and syntactic structure will ultimately balance each other out. This assumption remained unchallenged throughout the twentieth century, almost acquiring (more implicitly than explicitly, though) the status of an established truth, or even dogma. Only with linguistic sub-disciplines like language typology, Creolistics, corpus linguistics or dialectometry gaining full momentum, coupled with the strong quantitative turn since the 1990s, has the equi-complexity axiom come back in the limelight and can be investigated with the sophisticated theoretical and methodological toolkit of 21st-century linguistics. Besides structural (or: absolute) complexity, other major aspects of linguistic complexity and complexity metrics that have been discussed in the research literature of the last twenty years can be lumped together under the heading of user-based (or: relative) complexity. On the one hand, this includes the processing and interpretive efforts the natural language user needs to engage in when assigning meanings and functions to certain structural elements, patterns, and rules (in isolation or in actual usage) of their native or a different language or dialect. On the other hand, there are various lines of complexity research that focus on the learner, both the first-language child learner and, especially, the second or foreign-language adult learner. This take on linguistic complexity (discussed under the heading of learner complexity) is dominant in Second Language Acquisition (SLA) research but prominent, too, in relevant research informed by sociolinguistic and contact-linguistic perspectives. Finally, it is evident that for both structural and user-based complexity there is also research adopting an evolutionary (language change) or developmental (ontogenetic) perspective.