With or without a system: How category-specific and system-wide cognitive biases shape word order

There are certain recurrent features of language that characterise the way whole language systems are structured, and others that target specific categories of items within those wider systems. For example, languages tend to exhibit harmonic (i.e. consistent) ordering between heads and dependents, making it a kind of system-wide regularity. While this tendency is generally robust, some categories of linguistic items deviate from this trend. We examine one such case of non-harmony, namely the order of the noun with respect to two dependents -- adjectives and genitives. Using two silent gesture experiments, this study tests the hypothesis that category-specific cognitive biases favour postnominal adjective order and prenominal genitive order. Further, we show that the influence of these biases is revealed in contexts where no conventionalised system is in place. When a system is in place, participants learn that system, and category-specific biases do not impact their learning. Our results suggest that different types of linguistic contexts reveal the influence of separate types of cognitive biases, such that some are active during learning and others are active during language creation.