Children’s Interpretation of Additive Particles mo ‘also’ and also in Japanese and English Hisao Kurokami, Daniel Goodhue, Valentine Hacquard, and Jeffrey Lidz 1. Introduction * Additive particles like English also and Japanese mo ‘also’ contribute an additive presupposition to sentence meaning via their association with focus (König, 1991). For example, a speaker uttering the English sentence (1), which contains an object-associated also as indicated by pitch accent location, not only asserts that Mickey ate a banana but also presupposes that Mickey ate something other than a banana. Likewise, a speaker uttering the Japanese sentence in (2), which contains an object-associated mo as indicated by its post-object position in the sentence, makes the same assertion and presupposition. (1) Mickey also ate a BANANA. 1 (2) Mikki-wa banana-mo tabe-ta. 2 Mickey-TOP banana-also eat-PAST ‘Mickey also ate a BANANA’ Presuppositions consist of backgrounded information, whose truth is taken for granted by all discourse participants, i.e., they are part of the COMMON GROUND (Stalnaker, 1978). As such, additive particles like also typically require that the relevant information that satisfies (the truth of) the additive presupposition already be established as backgrounded information, prior to their use; if not, the use of the particles would be infelicitous. This is illustrated in example (3) below. (3) A: What did Mickey eat for lunch? a. B: # Mickey also ate a BANANA. b. B: Mickey ate an APPLE, and he also ate a BANANA. * Hisao Kurokami, Daniel Goodhue, Valentine Hacquard, and Jeffrey Lidz: University of Maryland. Corresponding author: Hisao Kurokami, kurokamihisao@gmail.com. 1 The use of capital letters in the linguistic example indicates the location of a pitch accent. 2 Unlike in English where a phonological cue plays a crucial role in determining focus- association, it is typically the case that focus-association is determined by a syntactic cue in Japanese, i.e., Japanese focus particles associate with the constituent they adjoin to. Specifically, post-object mo marks object-association. © 2021 Hisao Kurokami, Daniel Goodhue, Valentine Hacquard, and Jeffrey Lidz. Proceedings of the 45th annual Boston University Conference on Language Development, ed. Danielle Dionne and Lee-Ann Vidal Covas, 449-461. Somerville, MA: Cascadilla Press.