Comprehension of Degraded Speech Matures During Adolescence

Speech perception in noise, working memory, and attention in children: A scoping review

PURPOSE

Speech perception in noise is an everyday occurrence for adults and children alike. The factors that influence how well individuals cope with noise during spoken communication are not well understood, particularly in the case of children. This article aims to review the available evidence on how working memory and attention play a role in children's speech perception in noise, how characteristics of measures affect results, and how this relationship differs in non-typical populations.

METHOD

This article is a scoping review of the literature available on PubMed. Forty articles were included for meeting the inclusion criteria of including children as participants, some measure of speech perception in noise, some measure of attention and/or working memory, and some attempt to establish relationships between the measures. Findings were charted and presented keeping in mind how they relate to the research questions.

RESULTS

The majority of studies report that attention and especially working memory are involved in speech perception in noise by children. We provide an overview of the impact of certain task characteristics on findings across the literature, as well as how these affect non-typical populations.

CONCLUSION

While most of the work reviewed here provides evidence suggesting that working memory and attention are important abilities employed by children in overcoming the difficulties imposed by noise during spoken communication, methodological variability still prevents a clearer picture from emerging.

Perceptual Learning of Dysarthria in Adolescence

PURPOSE

As evidenced by perceptual learning studies involving adult listeners and speakers with dysarthria, adaptation to dysarthric speech is driven by signal predictability (speaker property) and a flexible speech perception system (listener property). Here, we extend adaptation investigations to adolescent populations and examine whether adult and adolescent listeners can learn to better understand an adolescent speaker with dysarthria.

METHOD

Classified by developmental stage, adult (n = 42) and adolescent (n = 40) listeners completed a three-phase perceptual learning protocol (pretest, familiarization, and posttest). During pretest and posttest, all listeners transcribed speech produced by a 13-year-old adolescent with spastic dysarthria associated with cerebral palsy. During familiarization, half of the adult and adolescent listeners engaged in structured familiarization (audio and lexical feedback) with the speech of the adolescent speaker with dysarthria; and the other half, with the speech of a neurotypical adolescent speaker (control).

RESULTS

Intelligibility scores increased from pretest to posttest for all listeners. However, listeners who received dysarthria familiarization achieved greater intelligibility improvements than those who received control familiarization. Furthermore, there was a significant effect of developmental stage, where the adults achieved greater intelligibility improvements relative to the adolescents.

CONCLUSIONS

This study provides the first tranche of evidence that adolescent dysarthric speech is learnable-a finding that holds even for adolescent listeners whose speech perception systems are not yet fully developed. Given the formative role that social interactions play during adolescence, these findings of improved intelligibility afford important clinical implications.

Children's syntactic parsing and sentence comprehension with a degraded auditory signal

During sentence comprehension, young children anticipate syntactic structures using early-arriving words and have difficulties revising incorrect predictions using late-arriving words. However, nearly all work to date has focused on syntactic parsing in idealized speech environments, and little is known about how children's strategies for predicting and revising meanings are affected by signal degradation. This study compares comprehension of active and passive sentences in natural and vocoded speech. In a word-interpretation task, 5-year-olds inferred the meanings of novel words in sentences that (1) encouraged agent-first predictions (e.g., The blicket is eating the seal implies The blicket is the agent), (2) required revising predictions (e.g., The blicket is eaten by the seal implies The blicket is the theme), or (3) weakened predictions by placing familiar nouns in sentence-initial position (e.g., The seal is eating/eaten by the blicket). When novel words promoted agent-first predictions, children misinterpreted passives as actives, and errors increased with vocoded compared to natural speech. However, when familiar words were sentence-initial that weakened agent-first predictions, children accurately interpreted passives, with no signal-degradation effects. This demonstrates that signal quality interacts with interpretive processes during sentence comprehension, and the impacts of speech degradation are greatest when late-arriving information conflicts with predictions.

Recognition of vocoded words and sentences in quiet and multi-talker babble with children and adults

A vocoder is used to simulate cochlear-implant sound processing in normal-hearing listeners. Typically, there is rapid improvement in vocoded speech recognition, but it is unclear if the improvement rate differs across age groups and speech materials. Children (8–10 years) and young adults (18–26 years) were trained and tested over 2 days (4 hours) on recognition of eight-channel noise-vocoded words and sentences, in quiet and in the presence of multi-talker babble at signal-to-noise ratios of 0, +5, and +10 dB. Children achieved poorer performance than adults in all conditions, for both word and sentence recognition. With training, vocoded speech recognition improvement rates were not significantly different between children and adults, suggesting that improvement in learning how to process speech cues degraded via vocoding is absent of developmental differences across these age groups and types of speech materials. Furthermore, this result confirms that the acutely measured age difference in vocoded speech recognition persists after extended training.

Autoscore: An open-source automated tool for scoring listener perception of speech

Speech perception studies typically rely on trained research assistants to score orthographic listener transcripts for words correctly identified. While the accuracy of the human scoring protocol has been validated with strong intra- and inter-rater reliability, the process of hand-scoring the transcripts is time-consuming and resource intensive. Here, an open-source computer-based tool for automated scoring of listener transcripts is built (Autoscore) and validated on three different human-scored data sets. Results show that not only is Autoscore highly accurate, achieving approximately 99% accuracy, but extremely efficient. Thus, Autoscore affords a practical research tool, with clinical application, for scoring listener intelligibility of speech.

Development of perception and perceptual learning for multi-timescale filtered speech

The perception of temporally changing auditory signals has a gradual developmental trajectory. Speech is a time-varying signal, and slow changes in speech (filtered at 0-4 Hz) are preferentially processed by the right hemisphere, while the left extracts faster changes (filtered at 22-40 Hz). This work examined the ability of 8- to 19-year-olds to both perceive and learn to perceive filtered speech presented diotically for each filter type (low vs high) and dichotically for preferred or non-preferred laterality. Across conditions, performance improved with increasing age, indicating that the ability to perceive filtered speech continues to develop into adolescence. Across age, performance was best when both bands were presented dichotically, but with no benefit for presentation to the preferred hemisphere. Listeners thus integrated slow and fast transitions between the two ears, benefitting from more signal information, but not in a hemisphere-specific manner. After accounting for potential ceiling effects, learning was greatest when both bands were presented dichotically. These results do not support the idea that cochlear implants could be improved by providing differentially filtered information to each ear. Listeners who started with poorer performance learned more, a factor which could contribute to the positive cochlear implant outcomes typically seen in younger children.