In Search of Salience: Focus Detection in the Speech of Different Talkers

Many different prosodic cues can help listeners predict upcoming speech. However, no research to date has assessed listeners’ processing of preceding prosody from different speakers. The present experiments examine (1) whether individual speakers (of the same language variety) are likely to vary in their production of preceding prosody; (2) to the extent that there is talker variability, whether listeners are flexible enough to use any prosodic cues signaled by the individual speaker; and (3) whether types of prosodic cues (e.g., F0 versus duration) vary in informativeness. Using a phoneme-detection task, we examined whether listeners can entrain to different combinations of preceding prosodic cues to predict where focus will fall in an utterance. We used unsynthesized sentences recorded by four female native speakers of Australian English who happened to have used different preceding cues to produce sentences with prosodic focus: a combination of pre-focus overall duration cues, F0 and intensity (mean, maximum, range), and longer pre-target interval before the focused word onset (Speaker 1), only mean F0 cues, mean and maximum intensity, and longer pre-target interval (Speaker 2), only pre-target interval duration (Speaker 3), and only pre-focus overall duration and maximum intensity (Speaker 4). Listeners could entrain to almost every speaker’s cues (the exception being Speaker 4’s use of only pre-focus overall duration and maximum intensity), and could use whatever cues were available even when one of the cue sources was rendered uninformative. Our findings demonstrate both speaker variability and listener flexibility in the processing of prosodic focus.

The Role of Talker Variability in Nonnative Phonetic Learning: A Systematic Review and Meta-Analysis

Purpose: High-variability phonetic training (HVPT) has been found to be effective on adult second language (L2) learning, but results are mixed in regards to the benefit of multiple talkers over single talker. This study provides a systematic review with meta-analysis to investigate the talker variability effect in nonnative phonetic learning and the factors moderating the effect. Method: We collected studies with keyword search in major academic databases including EBSCO, ERIC, MEDLINE, ProQuest Dissertations & Theses, Elsevier, Scopus, Wiley Online Library, and Web of Science. We identified potential participant-, training-, and study-related moderators and conducted a random-effects model meta-analysis for each individual variable. Results: On the basis of 18 studies with a total of 549 participants, we obtained a small-level summary effect size (Hedges' g = 0.46, 95% confidence interval [CI; 0.08, 0.84]) for the immediate training outcomes, which was greatly reduced ( g = −0.04, 95% CI [−0.46, 0.37]) after removal of outliers and correction for publication bias, whereas the effect size for immediate perceptual gains was nearly medium ( g = 0.56, 95% CI [0.13, 1.00]) compared with the nonsignificant production gains. Critically, the summary effect sizes for generalizations to new talkers ( g = 0.72, 95% CI [0.15, 1.29]) and for long-term retention ( g = 1.09, 95% CI [0.39, 1.78]) were large. Moreover, the training program length and the talker presentation format were found to potentially moderate the immediate perceptual gains and generalization outcomes. Conclusions: Our study presents the first meta-analysis on the role of talker variability in nonnative phonetic training, which demonstrates the heterogeneity and limitations of research on this topic. The results highlight the need for further investigation of the influential factors and underlying mechanisms for the presence or absence of talker variability effects. Supplemental Material https://doi.org/10.23641/asha.16959388

Talker variability shapes early word representations in English-learning 8-month-olds

Infants must form appropriately specific representations of how words sound, and what they mean. Previous research suggests that while 8-month-olds are learning words, they struggle with recognizing different-sounding instances of words (e.g. from new talkers), and with rejecting incorrect pronunciations. We asked how adding talker variability during learning may change infants' ability to learn and recognize words. Monolingual English-learning 7-to-9-month-olds heard a single novel word paired with an object in either a 'no variability','within talker variability' or 'between talker variability' habituation. We then tested whether infants formed appropriately specific representations by changing the talker (Experiment 1a) or mispronouncing the word (Experiment 2), and by changing the trained word or object altogether (both experiments). Talker variability influenced learning. Infants trained with no talker variability learned the word-object link, but failed to recognize the word trained by a new talker, and were insensitive to the mispronunciation. Infants trained with talker variability dishabituated only to the new object, exhibiting difficulty forming the word-object link. Neither pattern is adult-like. Results are reported for both in-lab and Zoom participants. Implications for the role of talker variability in early word learning are discussed.

Quantifying talker variability in North-American infant's daily input

Words sound slightly different each time they are said, both by the same talker and across talkers. Rather than hurting learning, lab studies suggest that talker variability helps infants learn similar sounding words. However, very little is known about how much variability infants hear within a single talker or across talkers in naturalistic input. Here, we quantified these types of talker variability for highly frequent words spoken to 44 infants, from naturalistic recordings sampled longitudinally over a year of life (from 6-17 months). We used non-contrastive acoustic measurements (e.g. mean pitch, duration, harmonics-to-noise ratio) and holistic measures of sound similarity (normalized acoustic distance) to quantify acoustic variability. We find three key results. First, pitch-based variability was generally lower for infants' top talker than across their other talkers, but overall acoustic distance is higher for tokens from the top talker vesus the others. Second, the amount of acoustic variability infants heard was not simply redundant with other properties of the input such as number of talkers or tokens, or proportion of speech from particular sources (e.g. women, children, electronics). Finally, we find that patterns of acoustic variability heard in naturalistic input were similar to those found with in-lab stimuli that facilitated word learning. This large-scale quantification of talker variability in infants' everyday input sets the stage for linking naturally-occurring variability ‘in the wild’ to early word learning.

Desirable difficulties in statistical learning? How talker variability impacts artificial grammar learning

Contending with talker variability has been found to lead to processing costs but also benefits by focusing learners on invariant properties of the signal. These discrepant findings may indicate that talker variability acts as a desirable difficulty. That is, talker variability may lead to initial costs followed by long term benefits for retention and generalization. Adult participants learned an artificial grammar affording learning of multiple components by 1-, 2- or 8- talkers, tested at 3 time points. The 8-talker condition did not impact learning. The 2-talker condition negatively impacted some aspects of learning, but only under more difficult learning conditions. Across both experiments, generalization of the grammatical dependency was difficult. Taken together, we discovered that high and limited talker variability differentially impact artificial grammar learning. However, talker variability does not act as a desirable difficulty in the current paradigm, as the few evidenced costs were not related to long-term benefits.