Timing is Stressful: Do Listeners Combine Meaning and Rhythm to Predict Speech?

English and other languages such as German are stress-timed languages: the timing of the speech is determined by stressed and unstressed syllables, providing structure for sentences. While natural speech is not generally metrically regular, like in Shakespearean poetry, it still conveys timing cues through stress. Prior research has found that metric regularity enhances the processing of words (Rothermich et al, 2012), potentially because it attunes listeners’ attention to the predictability of stressed, and therefore important, syllables. Other work (e.g., Rogers, 2017) has suggested that predictability in the form of semantic associations (e.g., hearing “barn” facilitates understanding of “hay”) is a driving force for speech understanding, so much so that people falsely “hear” words predicted by semantic context (e.g., hearing “barn” leads to hearing “hay”, even if “pay” was presented). In the current study, we aimed to examine how stress patterns and semantic associations may interact in listeners’ understanding of speech, as they both provide bases for predictions on the part of the listener. We measured speech understanding by masking the final word of a sentence in noise, then asking participants to identify what that word was (e.g., Jake visits the park to walk his DOG). We manipulated each sentence’s rhythmic predictability (whether the sentence was in natural speech, with a rhythm emphasized, or with a drum beat matching rhythm preceding the rhythmic speech) and semantic predictability (whether the last word made sense with the sentence, e.g. Jake visits the park to walk his dog/log). There was also a baseline condition for each of the rhythmic conditions wherein the sentence predictability was low. The results indicated that the beat prime improved processing of the rhythmic speech in conditions where expectancy effects played a role (semantically congruent and incongruent) but had a negligible impact in the baseline condition

Sensory Entrainment Mechanisms in Auditory Perception: Neural Synchronization Cortico-Striatal Activation.

The auditory system displays modulations in sensitivity that can align with the temporal structure of the acoustic environment. This sensory entrainment can facilitate sensory perception and is particularly relevant for audition. Systems neuroscience is slowly uncovering the neural mechanisms underlying the behaviorally observed sensory entrainment effects in the human sensory system. The present article summarizes the prominent behavioral effects of sensory entrainment and reviews our current understanding of the neural basis of sensory entrainment, such as synchronized neural oscillations, and potentially, neural activation in the cortico-striatal system

Effects of rhythm and phrase-final lengthening on word-spotting in Korean

A word-spotting experiment was conducted to investigate whether rhythmic consistency and phrase-final lengthening facilitate performance in Korean. Listeners had to spot disyllabic and trisyllabic words in nonsense strings organized in phrases with either the same or variable syllable count; phrase-final lengthening was absent, or occurring either in all phrases or only in the phrase immediately preceding the target. The results show that, for disyllabic targets, inconsistent syllable count and lengthening before the target led to fewer errors. For trisyllabic targets, accuracy was at ceiling, but final lengthening in all phrases reduced reaction times. The results imply that both rhythmic consistency (i.e. regular syllable count) and phrase-final lengthening play a role in word-spotting and, by extension, in speech processing in Korean, as in other languages. However, the results also reflect the language specific role of prosodic cues. First, the cues here were used primarily with disyllabic targets, which were cognitively more demanding to process partly due to their high phonological neighborhood density. Second, the facilitating effect of rhythmic consistency was weak, possibly because strict consistency is not present in spoken Korean. Overall, rhythmic consistency facilitated spotting when targets mapped onto phrases, confirming the importance of phrasal organization in Korean speech processing

The relationship between language production and verbal short-term memory: The role of stress grouping

This study investigates the influence of stress grouping on verbal short-term memory (STM). English speakers show a preference to combine syllables into trochaic groups, both lexically and in continuous speech. In two serial recall experiments, auditory lists of nonsense syllables were presented with either trochaic (STRONG-weak) or iambic (weak-STRONG) stress patterns, or in monotone. The acoustic correlates that carry stress were also manipulated in order to examine the relationship between input and output processes during recall. In Experiment 1, stressed and unstressed syllables differed in intensity and pitch but were matched for spoken duration. Significantly more syllables were recalled in the trochaic stress pattern condition than in the iambic and monotone conditions, which did not differ. In Experiment 2, spoken duration and pitch were manipulated but intensity was held constant. No effects of stress grouping were observed, suggesting that intensity is a critical acoustic factor for trochaic grouping. Acoustic analyses demonstrated that speech output was not identical to the auditory input, but that participants generated correct stress patterns by manipulating acoustic correlates in the same way in both experiments. These data challenge the idea of a language-independent STM store and support the notion of separable phonological input and output processes