With or Without a System: How Category-Specific and System-Wide Cognitive Biases Shape Word Order.

Certain recurrent features of language characterize the way a whole language system is structured. By contrast, others target specific categories of items within those wider systems. For example, languages tend to exhibit consistent order of heads and dependents across different phrases-a system-wide regularity known as harmony. While this tendency is generally robust, some specific syntactic categories appear to deviate from the trend. We examine one such case, the order of adjectives and genitives, which do not exhibit a typological tendency for consistent order with respect to the noun. Instead, adjectives tend to follow and genitives precede the noun. Across two silent gesture experiments, we test the hypothesis that these category-specific ordering tendencies reflect cognitive biases that favor (i) conveying objects before properties that modify them, but (ii) conveying expressions of possession before possessors. While our hypothesis is thus that these biases are semantic in nature-they impact preferences for how concepts are ordered-the claim is that they may have downstream effects on conventionalized syntax by contributing to an over-representation of postnominal adjectives and prenominal genitives. We find that these biases affect gesture order in contexts where no conventionalized 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 contexts reveal distinct types of cognitive biases; some are active during learning and others are active during language creation.