In this chapter I discuss different criteria and strategies related to the order of words, morphemes and syntactic constituents. There are very many theories, especially in psycholinguistics, which argue for some word orders being more costly than others. I argue that different ways of minimizing processing costs can be interpreted as maximization of accessibility, according to the general principles introduced in Chapter 1. First, I discuss which factors can, according to different researchers, make word order more or less costly, based on the existing evidence. Next, I provide well-known examples of efficiency and discuss competing explanations. The strategies include minimization of dependency distances and syntactic domains, putting Subject first, using a specific order of noun phrase elements and morphemes, Greenbergian word order correlations and avoidance of crossing dependencies, which can be explained by the preference for continuous constituents.

This chapter presents three case studies that demonstrate that accessibility based on predictability relationships between constructions and their lexical fillers plays a role in alternations with longer and shorter alternative forms. The alternations are help + (to) Infinitive, Verb (at) home and go (and) Verb. I formulate the Hypothesis of Construction–Lexeme and Formal Length, which predicts the longer variants to be used when the associations are weaker, and shorter forms when the associations are stronger. This study demonstrates that the probabilistic relationships between constructions and collexemes can explain the choice between the shorter and longer constructional variants, which needs to be integrated in Constructionist theory. Moreover, we also see many other manifestations of high and low accessibility that determine the use of longer and shorter variants. This shows that language users adjust their output to the individual situation in many very subtle ways, depending on semantic features, inflectional forms, distances between constructional components, and many other factors.

This chapter discusses types of efficiency beyond coding length asymmetries and word order. Language users have a preference for forms and meanings with higher accessibility, which can be understood broadly as ease of retrieval from long-term memory, transparency, or absence of nearby competitors. The strategies discussed in this chapter include analytic support, avoidance of identity and efficient introduction of new referents into discourse. Higher accessibility facilitates processing. This type of efficiency is the least explored one, and requires more research. In particular, we need to understand which aspects of accessibility facilitate processing, and how their preferences interact with other strategies, such as using longer forms for less accessible meanings.

This chapter presents evidence based on typological data, corpora and an artificial language learning experiment that supports the claim that form–meaning correspondences in causative constructions are best explained by the Principle of Communicative Efficiency. Other accounts which involve iconicity and productivity as explanatory factors are less successful in predicting and explaining the famous correlation between formal and semantic integration of events in causative constructions. Moreover, this account explains other form–meaning correspondences beyond event integration and the distinction between direct and indirect causation, such as intentional or accidental causation. Finally, this account predicts correctly the emergence of efficient formal asymmetries in an artificial language learning experiment.

As argued in Chapter 1, articulation is the slowest and most energy-consuming stage in human communication. The speaker can spare effort and time by omitting or shortening the forms that represent accessible information – that is, the information already available to the addressee, or easily inferable from the context and general knowledge. In contrast, more effort can be spent on information that is less accessible. We speak of an efficient length asymmetry when there is a negative correlation between formal length and accessibility of information. The chapter discusses diverse formal asymmetries that display this correlation – in lexicon, phonology, morphosyntax and discourse. Alternative explanations are also discussed.

The aim of this chapter is to provide the basic principles, examples and possible causal models of diachronic changes that lead to the emergence of efficient language structures. I argue that they are at least partly motivated by the pragmatic mechanisms and heuristics discussed in the previous chapters. This chapter provides diachronic evidence of efficient reduction and enhancement. Alternative explanations are also discussed. I offer an overview of influential theories that specify the causal mechanisms of language change leading to efficient formal and semantic changes, including grammaticalization. In addition, the chapter addresses the motivations for suppletive and compositional forms, emergence of efficient word order patterns and a more philosophical question about the role of teleology in explanations of language change.

The notion of efficient trade-offs is popular in studies of language from an efficiency perspective. These studies represent a valuable contribution to functional approaches to language. They provide interesting hypotheses for large-scale empirical investigations. At the same time, trade-offs can turn out to be oversimplifications when we focus only on correlations between two variables. The next step is to investigate causal (directional) networks with multiple factors that can influence language use and structure. A first attempt is shown in the case study of Subject and Object cues. We find that the correlation between word order freedom and case marking is robust and cannot be reduced to the effect of other linguistic cues. Also, the causal analyses suggest that the causal direction is more likely to be from word order to case marking than the other way round. At the same time, the evidence makes us conclude that the way efficiency is reflected in aggregate linguistic variables is anything but straightforward.

This chapter provides a summary of the main findings reported in this book and discusses numerous questions for future research. It also addresses the political aspects of communicative efficiency and contemplates the potential impact of new technologies on costs of language communication.