Infants must develop both flexibility and constraint in their interpretation of acceptable word forms. The current experiments examined the development of infants’ lexical interpretation of non-native variations in pitch contour. Fourteen, 17-, and 19-month-olds (Experiments 1 and 2, N = 72) heard labels for two novel objects; labels contained the same syllable produced with distinct pitch contours (Mandarin lexical tones). The youngest infants learned the label-object mappings, but the older groups did not, despite being able to discriminate pitch differences in an object-free task (Experiment 3, N = 14). Results indicate that 14-month-olds remain flexible regarding what sounds make meaningful distinctions between words. By 17–19 months, experience with a non-tonal native language constrains infants’ interpretation of lexical tone.

While research shows that adults attend to both segmental and suprasegmental regularities in speech, including syllabic transitional probabilities as well as stress and intonational patterns, little is known about how statistical learning operates given input from tonal languages. In the current study, we designed an artificial tone language to address several questions: can adults track regularities in a tonal language? Is learning enhanced by previous exposure to tone-marking languages? Does bilingualism affect learning in this task? To address these questions, we contrasted the performance of English monolingual adults (Experiment 1), Mandarin monolingual and Mandarin–English bilingual adults (Experiment 2), and non-tonal bilingual adults (Experiment 3) in a statistical learning task using an artificial tone language. The pattern of results suggests that while prior exposure to tonal languages did not lead to significant improvements in performance, bilingual experience did enhance learning outcomes. This study represents the first demonstration of statistical learning of an artificial tone language and suggests a complex interplay between prior language experience and subsequent language learning.

Recent research has begun to explore individual differences in statistical learning, and how those differences may be related to other cognitive abilities, particularly their effects on language learning. In the present research, we explored a different type of relationship between language learning and statistical learning: the possibility that learning a new language may also influence statistical learning by changing the regularities to which learners are sensitive. We tested two groups of participants, Mandarin Learners and Naïve Controls, at two time points, six months apart. At each time point, participants performed two different statistical learning tasks: an artificial tonal language statistical learning task and a visual statistical learning task. Only the Mandarin-learning group showed significant improvement on the linguistic task, while both groups improved equally on the visual task. These results support the view that there are multiple influences on statistical learning. Domain-relevant experiences may affect the regularities that learners can discover when presented with novel stimuli.

Infants are sensitive to statistical regularities (i.e., transitional probabilities, or TPs) relevant to segmenting words in fluent speech. However, there is debate about whether tracking TPs results in representations of possible words. Infants show preferential learning of sequences with high TPs (HTPs) as object labels relative to those with low TPs (LTPs). Such findings could mean that only the HTP sequences have a word-like status, and they are more readily mapped to a referent for that reason. But these findings could also suggest that HTP sequences are easier to encode, just like any other predictable sequence. Here we aimed to distinguish between these explanations. To do so, we built on findings that infants become resistant to learning labels that are not typical of their native language as they approach 2 years of age and add words to their lexicons. If tracking TPs in speech results in identifying candidate words, at this age TPs may have reduced power to confer lexical status when they yield a unit that is very dissimilar to word forms that are typical of infants' native language. Indeed, we found that at 20 months, English-learning infants with relatively small vocabularies learned HTP Italian words (but not LTP words) as object labels, while infants with larger vocabularies resisted learning HTP Italian words. These findings suggest that the HTP sequences may be represented as candidate words, and more broadly, that TP statistics are relevant to word learning.

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Many characters in written Chinese incorporate components (radicals) that provide cues to meaning. These cues are often partial, and some are misleading because they are unrelated to the character's meaning. Previous studies have shown that radicals influence the reader's processing of the characters in which they occur (e.g., Feldman & Siok, 1999). We investigated whether readers automatically activate the semantic information associated with a radical even when it is irrelevant to the character's meaning, using a modified version of the Van Orden (1987) task with auditory semantic relatedness ratings on test items. Fifty-one Mandarin speakers participated in the study. On each trial they saw a reference category such as "animal" prior to seeing a character then indicated whether the target character was a member of that category.Decisions were slower and less accurate when a target that is not a member of the target category contained a radical that is. For example, if the category is "found in the kitchen," the answer for the target 券 "ticket" is no; however the character contains the misleading radical 刀 "knife". These patterns suggest that readers process the semantics of the radical even when it is not relevant to the meaning of the character. The results further verify the role of radical semantics in character processing and raise questions as to whether repetitions of experience with the idiosyncrasies of the script may result in some of the irrelevant semantics influencing the meaning of the character.

Infant-directed speech (IDS) produced in laboratory settings contains acoustic cues, such as pauses, pitch changes, and vowel-lengthening that could facilitate breaking speech into smaller units, such as syntactically well-formed utterances, and the noun- and verb-phrases within them. It is unclear whether these cues are present in speech produced in more natural contexts outside the lab. We captured LENA recordings of caregiver speech to 12-month-old infants in daylong interactions (N = 49) to address this question. We found that the final positions of syntactically well-formed utterances contained greater vowel lengthening and pitch changes, and were followed by longer pauses, relative to non-final positions. However, we found no evidence that these cues were present at utterance-internal phrase boundaries. Results suggest that acoustic cues marking the boundaries of well-formed utterances are salient in everyday speech to infants and highlight the importance of characterizing IDS in a large sample of naturally-produced speech to infants.

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