Research Article: Learning and generalizing non-adjacent dependencies in 18-month-olds: A mechanism for language acquisition?

Date Published: October 11, 2018

Publisher: Public Library of Science

Author(s): Ileana Grama, Frank Wijnen, Antoni Rodriguez-Fornells.


The ability to track non-adjacent dependencies (the relationship between ai and bi in an aiXbi string) has been hypothesized to support detection of morpho-syntactic dependencies in natural languages (‘The princess is reluctantly kissing the frog’). But tracking such dependencies in natural languages entails being able to generalize dependencies to novel contexts (‘The general is angrily berating his troops’), and also tracking co-occurrence patterns between functional morphemes like is and ing (a class of elements that often lack perceptual salience). We use the Headturn Preference Procedure to investigate (i) whether infants are capable of generalizing dependencies to novel contexts, and (ii) whether they can track dependencies between perceptually non-salient elements in an artificial grammar aXb. Results suggest that 18-month-olds extract abstract knowledge of a_b dependencies between non-salient a and b elements and use this knowledge to subsequently re-familiarize themselves with specific ai_bi combinations. However, they show no evidence of generalizing ai_bi dependencies to novel aiYbi strings.

Partial Text

The remarkable ability of children to acquire their native language within a few years has often been attributed, at least partially, to their ability to detect distributional properties of the input. Distributional learning mechanisms have been successfully studied in both adult and infant populations. Thus, both adults [1] and infants [2] segment words from the input based on transitional probabilities between syllables, and use distributional cues to infer phonetic categories [3–4]. Both learn simple grammars and generalize those grammar rules to novel stimuli [5–6] and use frequent frames in the input (to___it) to infer lexical categories (to V it) [7–8]. Finally, both adults and infants detect the adjacent dependencies that determine phrase structure [9], and the non-adjacent dependencies that indicate more remote syntactic relationships [10–11]. The current study is concerned with the learning ability that allows both adults and infants to identify non-adjacent dependencies (NADs): co-occurrence patterns between elements that are non-adjacent in a sequence.

The ability to detect NADs in spoken input has been attested with infants as young as 15 months old [11], and has been hypothesized to contribute to the acquisition (starting from around 18 months [12]) of morpho-syntactic dependencies in natural languages.




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