To be able to recognize the

To be able to recognize the ungrammatical use of newly-learned words, toddlers must have proceeded in two steps. First, they Immunology Inflammation Compound Library had to learn the syntactic category of the novel word (i.e. noun or verb) during the training session. Second, as toddlers had never heard the newly-learned words preceded by the function word used at test (i.e. le), they had to exploit their knowledge of their native language syntax to compute which contexts are legal for each of the newly-learnt words and extrapolate this information during online syntactic processing. Note that the syntactic contexts used here were particularly complex, in that they featured an ambiguous function word, le, which could either be an article or an object clitic. Toddlers were thus able to use the syntactic context preceding an ambiguous function word to identify its role in the sentence and then build expectations regarding the syntactic category of the following content word. Children\'s sensitivity to the sentence structure of their language may hence be grammatical rather than solely distributional in nature from early on. For both toddlers and adults, ungrammatical sentences induced a sequence of two components, a late P600-like component and an early negativity. Both components were very similar in toddlers and adults. The P600 effect surfaced in both populations as a central positivity, and was delayed by about 150ms in toddlers relative to adults, which is not surprising (Atchley et al., 2006; Hahne et al., 2004; Holcomb et al., 1992). The early effect surfaced in both populations as a left-lateralized early negativity, resembling a LAN, with overlapping topographies and time-windows. The only difference between toddlers and adults comes from the finding that toddlers exhibited similar responses on both newly-learned and well-known words, while in adults newly-learned words did not show the early effect. This may be due to either or both of the following factors: First, adults learned the novel words just before the experiments, while toddlers had the opportunity to sleep between the learning and the test sessions, and sleep is known to consolidate lexical knowledge (Davis and Gaskell, 2009; Friedrich et al., 2015). Second, toddlers are used to learning novel words every day, and had yet to build a lexical entry for the referents that were used, whereas word learning is a more unusual activity for adults, who in addition had already stored a competing lexical item for the referents. Overall, the presence of this LAN-like early effect, a component often observed in the context of phrase structure violations that can be detected on the basis of a fast template-matching process, suggests that the computation of syntactic category expectations is fast and robust in toddlers, as Fate map is in adults. The early latency of the first grammaticality effect raises interesting questions regarding the time course of grammatical processing in young children. Specifically, as the entire effect (observed between 100 and 400ms after the onset of the critical word) develops before the end of the critical words (average word duration: 405ms), this suggests that the misplacement of the critical word is noticed extremely fast. That is, after hearing as little as just the first few phonemes of a content word, children can infer whether or not this word is correctly placed in the sentence context. Specific features of our experimental paradigm may have promoted this extremely fast processing. Each story featured only two protagonists performing a small number of actions and these stories were narrated using a very limited number of nouns and verbs. Because each story typically only contained 3–5 content words, anticipating the syntactic category of the next word in the sentence may have allowed toddlers to restrict their expectations to a very small number of specific words (typically 1 or 2 only). For this reason, hearing the initial phoneme of the critical item was sufficient to determine whether the unfolding word matched the expected lexical item (see Connolly and Phillips, 1994, for a similar effect in adults). Note, however, that although the minimal selection of words may have helped toddlers’ anticipation of the specific content words, restriction of the set could only be achieved once children had computed the structure of the phrase and inferred the category of the upcoming word.