When Japanese learners read "cats," do they automatically know it means more than one?

What is it about?

In English, adding -s to a noun signals "more than one" — but does that signal register automatically in the minds of learners whose native language (Japanese) works very differently? This study had 96 Japanese learners and 32 native English speakers read sentences word by word and, at unpredictable moments, quickly judge whether one or two words appeared on screen. Because a plural word like cats carries a "more than one" meaning, that meaning was expected to slow down the judgment — a Stroop-like interference. The key finding: Japanese learners were slowed by plural nouns, just like native speakers, suggesting the plural morpheme is automatically activating its meaning. A second twist emerged with singulars: neither group was slowed by the cat, but they diverged when singularity was made more explicit — native speakers were slowed by a cat, while learners were slowed by one cat instead.

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Why is it important?

Most prior research on plural morpheme acquisition asked whether learners notice errors in sentences — a method that bundles together knowledge of the morpheme itself with the ability to compute grammatical agreement, making it impossible to pinpoint where learning breaks down. This study decouples those two things by measuring whether the plural morpheme automatically triggers its meaning during ordinary reading, independent of any agreement computation. The result directly challenges the Morphological Congruency Hypothesis — a widely cited theory predicting that Japanese learners should struggle precisely because Japanese lacks obligatory plural marking — and reframes where L2 learners' real difficulty lies: not in connecting -s to "more than one," but likely in the downstream process of using that information to compute syntactic agreement.

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