Word Order Predicts Cross-Linguistic Differences in the Production of Redundant Color and Number Modifiers

When asked to identify objects having unique shapes and colors among other objects, English speakers often produce redundant color modifiers ("the red circle") while Spanish speakers produce them less often ("el circulo (rojo)"). This cross-linguistic difference has been attributed to a difference in word order between the two languages, under the incremental efficiency hypothesis (Rubio-Fernández, Mollica, & Jara-Ettinger, 2020). However, previous studies leave open the possibility that broad language differences between English and Spanish may explain this cross-linguistic difference such that English speakers may generally produce more modifiers than Spanish speakers, including redundant ones, irrespective of word order. Here, we test the incremental efficiency hypothesis in a language production task crossing language (English, Spanish) with modifier type (color, number). Critically, number words occur on the same side of the noun in both English and Spanish. If broad language differences are responsible for the higher rate of color word production in English compared to Spanish, then the same effect should hold for number words. In contrast, the incremental efficiency hypothesis predicts an interaction between language and modifier type, due to different ordering for color words but identical ordering for number words. Our pre-registered analyses offer strong support for the incremental efficiency hypothesis, demonstrating how seemingly small differences in language can cause us to describe the world in surprisingly different ways.