We aimed at testing young children, but started with a group of adults in order to get feedback on the design. The data of this control group (or pilot) are now reported in the main text of the manuscript.
Since we based our design on the one used by de Carvalho, Babineau, Trueswell, & Christophe (2019), we added the results of their pilot with 10 adults (5 in each condition) on this OSF page. The figure can be found in our result folder. Adults hearing a real function word (a pronoun or a determiner) co-occurring with a novel content word (Regarde, Une dase 'Look! A dase!' or Regarde, elle dase 'Look! She is dasing') had no problem looking at the correct interpretation (a novel action or a novel object). These results were not reported in the original paper, but together with ours, they support our interpretation of the current data. That is, the eye-gaze data of the adults tested for de Carvalho et al. (2019) were close to ceiling, but our data with a novel function word were not (although the two groups significantly differed from one another). Hence, both children and adults found it challenging to learn in an implicite task a novel function word, even if it behaved like the pronouns or the determiners in their native language. They nonetheless successfully managed to use 'ko', to allocate their visual attention towards the correct video (i.e. subjects in the Verb condition looked more and pointed more toward the novel action than subjects in the Noun condition).
