How does interaction affect categorization, and how might this vary between native and non-native speakers? Whenpeople use shared labels to categorize objects, they categorize more similarly to each other. We investigated whether interactionleads non-native speakers to categorize in the same way as native speakers. In six rounds, L1-English and L2-English/L1-Mandarin speakers individually categorized dishware using labels (BOWL, PLATE), then discussed their categories or anunrelated topic after each round. L2 speakers’ categories shifted following category-relevant interaction with L1 speakers, buttheir categories did not become more L1-like. Unexpectedly, category-relevant interaction reduced alignment within pairs andwithin language groups; however, this effect was weaker in the L2 than L1 group. Hence, L2 speakers showed a strongertendency than L1 speakers to use categories that were similar to other speakers from their language group. This suggests thatinteraction in an L2 can reinforce L2 speakers’ categories in their L1.

What is the mechanism by which linguistic knowledge is updated over time? In six experiments, we asked whether error-driven learning can explain how adults and children add new words to their vocabulary. Participants were exposed tonovel object labels that were more or less unexpected given participants linguistic knowledge. Two-to-four-year-olds werestrongly affected by expectations based on contextual constraint when choosing the referent of a new label. However,while adults formed stronger memory traces for novel words that violated a stronger prior expectation, childrens memorywas unaffected by the strength of their prior expectations. We conclude that the encoding of new words in memory followsthe principles of error-driven learning in adults, but not in preschoolers.

Novel labels provide feedback that may enhance categoricalalignment between interlocutors. However, the nature of thisfeedback may not always be linguistic. Lupyan (2008) hasdemonstrated the effects of labels on individualcategorization, and even non-word labels have seeminglyproduced greater consistency in sorting strategies (Lupyan &Casasanto, 2014). We extend this to alignment bydemonstrating that arbitrary labels can increase sortingconsistency to bring people’s categories closer together, evenwithout dialogue. Importantly, we argue that increasedalignment is not always due to labeling in a linguistic sense.Results suggest that it is not the content of the non-wordlabels driving the alignment effects, but the very presence ofthe labels acting as ‘anchors’ for category formation. Thisdemonstrates a more general cognitive effect of arbitrarylabels on categorization.

Syntactic priming occurs when structural information from one sentence influences processing of a subsequently encountered sentence (Bock, 1986; Ledoux et al., 2007). This article reports 2 eye-tracking experiments investigating the effects of a prime sentence on the processing of a target sentence that shared aspects of syntactic form. The experiments were designed to determine the degree to which lexical overlap between prime and target sentences produced larger effects, comparable to the widely observed "lexical boost" in production experiments (Pickering & Branigan, 1998; Pickering & Ferreira, 2008). The current experiments showed that priming effects during online comprehension were in fact larger when a verb was repeated across the prime and target sentences (see also Tooley et al., 2009). The finding of larger priming effects with lexical repetition supports accounts under which syntactic form representations are connected to individual lexical items (e.g., Tomasello, 2003; Vosse & Kempen, 2000, 2009).