Abstract
From an early age, exposure to a spoken language has allowed us to implicitly capture the structure underlying the succession of speech sounds in that language and to segment it into meaningful units (words). Statistical learning (SL), the ability to pick up patterns in the sensory environment without intention or reinforcement, is thus assumed to play a central role in the acquisition of the rule-governed aspects of language, including the discovery of word boundaries in the continuous acoustic stream. Although extensive evidence has been gathered from artificial languages experiments showing that children and adults are able to track the regularities embedded in the auditory input, as the probability of one syllable to follow another syllable in the speech stream, the developmental trajectory of this ability remains controversial. In this work, we have collected Event-Related Potentials (ERPs) while 5-year-old children and young adults (university students) were exposed to a speech stream made of the repetition of eight three-syllable nonsense words presenting different levels of predictability (high vs. low) to mimic closely what occurs in natural languages and to get new insights into the changes that the mechanisms underlying auditory statistical learning (aSL) might undergo through the development. The participants performed the aSL task first under implicit and, subsequently, under explicit conditions to further analyze if children take advantage of previous knowledge of the to-be-learned regularities to enhance SL, as observed with the adult participants. These findings would also contribute to extend our knowledge of the mechanisms available to assist SL at each developmental stage. Although behavioral signs of learning, even under explicit conditions, were only observed for the adult participants, ERP data showed evidence of online segmentation in the brain in both groups, as indexed by modulations in the N100 and N400 components. A detailed analysis of the neural data suggests, however, that adults and children rely on different mechanisms to assist the extraction of word-like units from the continuous speech stream, hence supporting the view that SL with auditory linguistic materials changes through development.
Highlights
A large number of studies have shown that the ability to extract regularities from the sensory environment, an ability known as statistical learning (SL; Saffran et al, 1996), is observed in young children (e.g., Saffran et al, 1996; Teinonen et al, 2009; Arciuli and Simpson, 2011; Bertels et al, 2015; Bosseler et al, 2016; Choi et al, 2020) and adults (e.g., Saffran et al, 1997; Fiser and Aslin, 2002; Turk-Browne et al, 2009; Johnson et al, 2020), little is known about how this ability changes through development
The results showed that 2-AFC performance exceeded the chance level for the low-transitional probability (TP) “words,” t(20) = 2.264, p = 0.015 in the implicit condition, and for the high-TP words, t(20) = 2.592, p = 0.017, and low-TP “words,” t(20) = 3.543, p = 0.002 in the explicit condition
The results obtained from the repeated measures ANOVA showed a main effect of group, F(1,39) = 4.791, p = 0.035, η2p = 0.109, pw = 0.569, indicating, unsurprisingly, that adults outperformed children (58.1 vs. 50.8%, respectively) when both tasks were taken as a whole
Summary
A large number of studies have shown that the ability to extract regularities from the sensory environment, an ability known as statistical learning (SL; Saffran et al, 1996), is observed in young children (e.g., Saffran et al, 1996; Teinonen et al, 2009; Arciuli and Simpson, 2011; Bertels et al, 2015; Bosseler et al, 2016; Choi et al, 2020) and adults (e.g., Saffran et al, 1997; Fiser and Aslin, 2002; Turk-Browne et al, 2009; Johnson et al, 2020), little is known about how this ability changes through development.This occurs, at least in part, because early works on SL, as well as in the implicit learning (IL)-related field (see Christiansen (2019)), claimed that SL/IL is an early-maturing ability that remains quite stable across development as no differences in performance had been observed between children and adults in those pioneering works (e.g., Reber, 1989, 2013; Saffran et al, 1997). A large number of studies have shown that the ability to extract regularities from the sensory environment, an ability known as statistical learning (SL; Saffran et al, 1996), is observed in young children (e.g., Saffran et al, 1996; Teinonen et al, 2009; Arciuli and Simpson, 2011; Bertels et al, 2015; Bosseler et al, 2016; Choi et al, 2020) and adults (e.g., Saffran et al, 1997; Fiser and Aslin, 2002; Turk-Browne et al, 2009; Johnson et al, 2020), little is known about how this ability changes through development. When instead of auditory syllables the authors used familiar sounds in the aSL task, Shufaniya and Arnon (2018) found evidence of SL improvements in children in both modalities These findings strongly suggest that SL is not age-invariant, as claimed by earlier works (Reber, 1989, 2013; Saffran et al, 1997), except for auditory linguistic materials. They agree with other works claiming, on one hand, that the extraction of regularities from the speech environment is a powerful mechanism for language acquisition (see Romberg and Saffran, 2010), and, on the other hand, that against what occurs in most cognitive skills, adults are not better than children at learning new languages (Thiessen et al, 2016; Smalle et al, 2017)
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