Are Words Easier to Learn From Infant‐ Than Adult‐Directed Speech? A Quantitative Corpus‐Based Investigation

Abstract

We investigate whether infant-directed speech (IDS) could facilitate word form learning when compared to adult-directed speech (ADS). To study this, we examine the distribution of word forms at two levels, acoustic and phonological, using a large database of spontaneous speech in Japanese. At the acoustic level we show that, as has been documented before for phonemes, the realizations of words are more variable and less discriminable in IDS than in ADS. At the phonological level, we find an effect in the opposite direction: The IDS lexicon contains more distinctive words (such as onomatopoeias) than the ADS counterpart. Combining the acoustic and phonological metrics together in a global discriminability score reveals that the bigger separation of lexical categories in the phonological space does not compensate for the opposite effect observed at the acoustic level. As a result, IDS word forms are still globally less discriminable than ADS word forms, even though the effect is numerically small. We discuss the implication of these findings for the view that the functional role of IDS is to improve language learnability.

Segmentability Differences Between Child-Directed and Adult-Directed Speech: A Systematic Test With an Ecologically Valid Corpus

“…To conclude, we found that advantages in segmentability for CDS over ADS in an ecological corpus were smaller and more inconsistent than previous estimations based on laboratory CDS–ADS. Overall, our word segmentation results align with other work on sound discriminability (Martin et al, 2015) and word discriminability (Guevara-Rukoz et al, 2018), suggesting that the high learnability attributed to CDS may have been overestimated. Research assessing the learnability properties of child-directed speech at other levels (e.g., syntax) would benefit from using similarly natural corpora, as well as a variety of algorithmic approaches.…”

“…Although children are exposed to both child-directed speech (CDS) and adult-directed speech (ADS), children appear to extract more information from the former than the latter (e.g., Cristia, 2013; Shneidman & Goldin-Meadow, 2012). This has led some to propose that most or all linguistic phenomena are more easily learned from CDS than ADS (e.g., Fernald, 2000), with a flurry of empirical literature examining specific phenomena (see Guevara-Rukoz et al, 2018, for a recent review). Deciding whether the learnability of linguistic units is higher in CDS than ADS is difficult for at least two reasons: It is difficult to find appropriate CDS and ADS corpora; and one must have an idea of how children learn to check whether such a strategy is more successful in one register than the other.…”

“…Several differences between CDS and ADS could affect word segmentation learnability. Caregivers may speak in a more variable pitch, leading both to increased arousal in the child (which should boost attention and overall performance; Thiessen, Hill, & Saffran, 2005) but also increased acoustic variability (which makes word identification harder; Guevara-Rukoz et al, 2018). To study word segmentation controlling for other differences (e.g., attention capture, fine-grained acoustics), we use computational models of word segmentation from phonologized transcripts.…”

Nasal Consonant Discrimination in Infant- and Adult-Directed Speech

“…While at segmental level no advantage of IDS was observed, when looking at other linguistic levels, for instance prosodic boundary detection [24] or lexical segmentation [25], IDS does have an advantage. Nevertheless, when combining both acoustic and lexical information for word form learning, an overall detrimental effect for IDS was obtained [26].…”

Density and Distinctiveness in Early Word Learning: Evidence From Neural Network Simulations

“…This behavior is generally adaptive because stored word sound memories and related perceptual mechanisms must be flexible enough to support cross‐contextual comprehension on the fly, for instance when a learner encounters a known word in an unfamiliar dialect (Church & Fisher, ). Furthermore, the number of minimally different words that young children know and hear regularly in the speech directed to them is limited (Guevara‐Rukoz et al, ), and this makes it reasonable to classify a novel sound sequence that is very similar to a known word as an instance of that known word instead of as an instance of an unknown word (Swingley & Aslin, ).…”