Auditory word comprehension is less incremental in isolated words

Speech input is often understood to trigger rapid and automatic activation of successively higher-level representations for comprehension of words. Here we show evidence from magnetoencephalography that incremental processing of speech input is limited when words are heard in isolation as compared to continuous speech. This suggests a less unified and automatic process than is often assumed. We present evidence that neural effects of phoneme-by-phoneme lexical uncertainty, quantified by cohort entropy, occur in connected speech but not isolated words. In contrast, we find robust effects of phoneme probability, quantified by phoneme surprisal, during perception of both connected speech and isolated words. This dissociation rules out models of word recognition in which phoneme surprisal and cohort entropy are common indicators of a uniform process, even though these closely related information-theoretic measures both arise from the probability distribution of wordforms consistent with the input. We propose that phoneme surprisal effects reflect automatic access of a lower level of representation of the auditory input (e.g., wordforms) while cohort entropy effects are task-sensitive, driven by a competition process or a higher-level representation that is engaged late (or not at all) during the processing of single words.

The Effects of a Parent-Implemented Language Intervention on Late-Talkers’ Expressive Skills: The Mediational Role of Parental Speech Contingency and Dialogic Reading Abilities

Several qualitative and quantitative features of parental speech input support children’s language development and may play a critical role in improving such process in late talkers. Parent-implemented interventions targeting late-talkers have been developed to promote children’s language outcomes by enhancing their linguistic environment, i.e., parental speech input. This study investigated the effect of a parent-implemented intervention in increasing late talkers’ expressive skills through modifications in structural and functional features of parental speech input. Forty-six thirty-one-month-old late talkers differing in their birth condition (either low-risk preterm or full-term) participated in the study with a parent; 24 parent-child dyads received a parent-implemented intervention centered on dialogic reading and focused stimulation techniques, whereas the other 22 dyads constituted the control group. At pre- and post-intervention, dyads took part in a parent-child shared book-reading session and both parental and child’s speech measures were collected and examined. Results showed that the intervention positively affected parents’ use of responses and expansions of children’s verbal initiatives, as well as the parental amount of talking over reading, whereas no structural features of parental input resulted modified. Mediation analyses pointed out that the intervention indirectly enhanced late-talkers’ use of verbal types and tokens through changes in parental use of expansions and amount of talking over reading. As birth status was entered as a covariate in the analysis, these findings can be extended to children with different gestational age. We conclude that the parent-implemented intervention was effective in supporting late-talkers’ gains in language development as a cascade result of the improvements in parental contingency and dialogic reading abilities. These promising findings suggest to examine not only children and parental outcomes but also the intervention mechanisms promoting changes in late-talkers’ language development as a clearer view on such process can inform the development of feasible, ecological and effective programs.

An oscillating computational model can track pseudo-rhythmic speech by using linguistic predictions

Neuronal oscillations putatively track speech in order to optimize sensory processing. However, it is unclear how isochronous brain oscillations can track pseudo-rhythmic speech input. Here we propose that oscillations can track pseudo-rhythmic speech when considering that speech time is dependent on content-based predictions flowing from internal language models. We show that temporal dynamics of speech are dependent on the predictability of words in a sentence. A computational model including oscillations, feedback, and inhibition is able to track pseudo-rhythmic speech input. As the model processes, it generates temporal phase codes, which are a candidate mechanism for carrying information forward in time. The model is optimally sensitive to the natural temporal speech dynamics and can explain empirical data on temporal speech illusions. Our results suggest that speech tracking does not have to rely only on the acoustics but could also exploit ongoing interactions between oscillations and constraints flowing from internal language models.

Individual Differences in the Use of Acoustic-Phonetic Versus Lexical Cues for Speech Perception

Previous research suggests that individuals with weaker receptive language show increased reliance on lexical information for speech perception relative to individuals with stronger receptive language, which may reflect a difference in how acoustic-phonetic and lexical cues are weighted for speech processing. Here we examined whether this relationship is the consequence of conflict between acoustic-phonetic and lexical cues in speech input, which has been found to mediate lexical reliance in sentential contexts. Two groups of participants completed standardized measures of language ability and a phonetic identification task to assess lexical recruitment (i.e., a Ganong task). In the high conflict group, the stimulus input distribution removed natural correlations between acoustic-phonetic and lexical cues, thus placing the two cues in high competition with each other; in the low conflict group, these correlations were present and thus competition was reduced as in natural speech. The results showed that 1) the Ganong effect was larger in the low compared to the high conflict condition in single-word contexts, suggesting that cue conflict dynamically influences online speech perception, 2) the Ganong effect was larger for those with weaker compared to stronger receptive language, and 3) the relationship between the Ganong effect and receptive language was not mediated by the degree to which acoustic-phonetic and lexical cues conflicted in the input. These results suggest that listeners with weaker language ability down-weight acoustic-phonetic cues and rely more heavily on lexical knowledge, even when stimulus input distributions reflect characteristics of natural speech input.

Early consonant production in Tseltal and Yélî Dnye

Recent evidence shows that children reach expected basic linguistic milestones in two rural Indigenous communities, Tseltal and Yélî Dnye, despite infrequent exposure to child-directed speech. However, those results were partly based on vocal maturity measures that are fairly robust to environmental variation, e.g. the onset of babbling. Directed speech input has been traditionally linked to lexical development, which is by contrast environmentally sensitive. We investigate the relation between child-directed speech and early phonological development in these two communities, focusing on a phonological benchmark that links children’s pre-lexical and early lexical development: the production of consonants. We find that, while Tseltal and Yélî children’s canonical babble onset align with previously attested patterns, their early consonant acquisition shows some divergence from prior expectations. These preliminary results suggest that early consonant production may demonstrate greater environmental sensitivity than canonical babble, possibly via similar mechanisms that link linguistic input and lexical development.