Speakers of two languages have access to two semantic systems that, while largely similar, may differ in subtleways. The existence of multiple similar systems offers the potential for comparison of their structures and discovery of thedifferences between them. We hypothesized that if bilinguals engage in such a comparison process, they may be (a) less likelythan monolinguals to view the categories of any single language as natural kinds, and (b) more likely than monolinguals todiscern differences among high-similarity items more generally. Monolingual and bilingual participants indicated their level ofagreement with statements equating social categories with natural kinds and judged the similarity of pairs of perceptual rela-tions. Compared to monolinguals, bilinguals were less willing to endorse naturalness statements and showed more variability intheir similarity judgments. These results suggest that bilingualism may promote sensitivity to differences among highly similarstimuli, linguistic and otherwise.

Psychological essentialism is the belief that members of a category share deep, underlying commonalities. Previous evidence suggests that essentialism is stronger for masculine than feminine properties and more evident in monolingual than bilingual children. Here, we investigated essentialism of gender by monolingual and bilingual adults, focusing on two distinct dimensions of essentialism: naturalness (regarding categories as natural kinds) and entitativity (regarding categories as homogeneous groups). Participants indicated their agreement with statements assessing beliefs about men and women on these two dimensions. The results replicated previous work showing that men are essentialized more than women, but revealed that this effect may be specific to the entitativity dimension. We also found that, compared to monolinguals, bilinguals were less likely to essentialize gender in terms of naturalness. Our findings converge with previous research highlighting the bidimensionality of essentialism and suggest that early effects of language experience on essentialist beliefs may persist into adulthood.