While theories on predictive processing posit that predictions are based on one’s prior experiences, experimental work has effectively ignored the fact that people differ from each other in their linguistic experiences and, consequently, in the predictions they generate. We examine usage-based variation by means of three groups of participants (recruiters, job-seekers, and people not (yet) looking for a job), two stimuli sets (word sequences characteristic of either job ads or news reports), and two experiments (a Completion task and a Voice Onset Time task). We show that differences in experiences with a particular register result in different expectations regarding word sequences characteristic of that register, thus pointing to differences in mental representations of language. Subsequently, we investigate to what extent different operationalizations of word predictability are accurate predictors of voice onset times. A measure of a participant’s own expectations proves to be a significant predictor of processing speed over and above word predictability measures based on amalgamated data. These findings point to actual individual differences and highlight the merits of going beyond amalgamated data. We thus demonstrate that is it feasible to empirically assess the variation implied in usage-based theories, and we advocate exploiting this opportunity.

The likelihood with which language users insert optional words or morphemes that explicitly mark syntactic structure tends to increase in complex grammatical environments. This positive correlation between explicitness and complexity, best known as the Complexity Principle, has been observed for a multitude of case studies in both naturally occurring language and experimental settings. Researchers have sought the explanation for this Complexity Principle in three different domains: cognitive comprehension processing, the language channel, and cognitive production processing. Based on these accounts, we formulate predictions regarding the action radius of the Complexity Principle in the alternation between a direct and prepositional object of the Dutch verb zoeken ‘search’. These predictions are tested against corpus observations. Our results confirm accounts according to which optional elements indicate production difficulties, as well as those that explain the Principle as a result of restrictions on the language channel. In addition, our results indicate that the Principle is sensitive to context-determined restrictions that are the result of its underlying cause. This may present a possible caveat for alternation studies.

Engagement systems encode the relative accessibility of an entity or state of affairs to the speaker and addressee, and are thus underpinned by our social cognitive capacities. In our first foray into engagement (Part 1), we focused on specialised semantic contrasts as found in entity-level deictic systems, tailored to the primal scenario for establishing joint attention. This second paper broadens out to an exploration of engagement at the level of events and even metapropositions, and comments on how such systems may evolve. The languages Andoke and Kogi demonstrate what a canonical system of engagement with clausal scope looks like, symmetrically assigning ‘knowing’ and ‘unknowing’ values to speaker and addressee. Engagement is also found cross-cutting other epistemic categories such as evidentiality, for example where a complex assessment of relative speaker and addressee awareness concerns the source of information rather than the proposition itself. Data from the language Abui reveal that one way in which engagement systems can develop is by upscoping demonstratives, which normally denote entities, to apply at the level of events. We conclude by stressing the need for studies that focus on what difference it makes, in terms of communicative behaviour, for intersubjective coordination to be managed by engagement systems as opposed to other, non-grammaticalised means.