Phonology, Semantics, and the Comprehension-Expression Gap in Emerging Lexicons.

Purpose Children come to understand many words by the end of their 1st year of life, and yet, generally by 12 months, only a few words are said. In this study, we investigated which linguistic factors contribute to this comprehension-expression gap the most. Specifically, we asked the following: Are phonological neighborhood density, semantic neighborhood density, and word frequency (WF) significant predictors of the probability that words known (understood) by children would appear in their spoken lexicons? Method Monosyllabic words in the active (understood and said) and passive (understood, not said) lexicons of 201 toddlers were extracted from the Dutch Communicative Development Inventory (Zink & Lejaegere, 2002) parent-completed forms. A generalized linear mixed-effects model was applied to the data. Results Phonological neighborhood density and WF were independently and significantly associated with whether or not a known word would be in children's spoken lexicons, but semantic neighborhood density was not. There were individual differences in the impact of WF on the probability that known words would be said. Conclusion The novel findings reported here have 2 major implications. First, they indicate that the comprehension-expression gap exists partly because the phonological distributional properties of words determine how readily words can be phonologically encoded for word production. Second, there are likely subtle and complex individual differences in how and when the statistical properties of the ambient language impact on children's emerging lexicons that might best be explored via longitudinal sampling of word knowledge and use.

Gleaning Structure from Sound: The Role of Prosodic Contrast in Learning Non-adjacent Dependencies.

The ability to detect non-adjacent dependencies (i.e. between a and b in aXb) in spoken input may support the acquisition of morpho-syntactic dependencies (e.g. The princess is kiss ing the frog). Functional morphemes in morpho-syntactic dependencies are often marked by perceptual cues that render them distinct from lexical elements. We use an artificial grammar learning experiment with adults to investigate the role of perceptual cues in non-adjacent dependency learning, by manipulating the perceptual/prosodic properties of the a / b elements in aXb strings and testing participants' incidental learning of these dependencies. Our results show that non-adjacent dependencies are learned both when the dependent elements are perceptually prominent, and when they are perceptually reduced compared to the intervening material (in the same way that functional words are reduced compared to lexical words), but only if integrated into a natural prosodic contour. This result supports the idea that the prosodic properties of natural languages facilitate non-adjacent dependency learning.

Non-adjacent dependency learning in infants at familial risk of dyslexia.

This study tests the hypothesis that developmental dyslexia is (partly) caused by a deficit in implicit sequential learning, by investigating whether infants at familial risk of dyslexia can track non-adjacent dependencies in an artificial language. An implicit learning deficit would hinder detection of such dependencies, which mark grammatical relations (e.g. between 'is' and '-ing' in 'she is happily singing'). In a head-turn experiment with infants aged 1;6, family risk and typically developing infants were exposed to one of two novel languages containing dependencies of the type a-X-c, b-X-d or a-X-d, b-X-c, with fixed first and third elements and twenty-four different X elements. During test, typically developing children listened longer to ungrammatical strings (i.e. that did not correspond to their training language). However, family-risk children did not discriminate between grammatical and ungrammatical strings, indicating deficient implicit learning. The implications of these findings in relation to dyslexia and other language-based disorders are discussed.