Cross-channel amplitude sweeps are crucial to speech intelligibility

Classical views of speech perception argue that the static and dynamic characteristics of spectral energy peaks (formants) are the acoustic features that underpin phoneme recognition. Here we use representations where the amplitude modulations of sub-band filtered speech are described, precisely, in terms of co-sinusoidal pulses. These pulses are parameterised in terms of their amplitude, duration and position in time across a large number of spectral channels. Coherent sweeps of energy across this parameter space are identified and the local transitions of pulse features across spectral channels are extracted. Synthesised speech based on manipulations of these local amplitude modulation features was used to explore the basis of intelligibility. The results show that removing changes in amplitude across channels has a much greater impact on intelligibility than differences in sweep transition or duration across channels. This finding has severe implications for future experimental design in the fields of psychophysics, electrophysiology and neuroimaging.     

Stopping speech suppresses the task-irrelevant hand

Some situations require one to quickly stop an initiated response. Recent evidence suggests that rapid stopping engages a mechanism that has diffuse effects on the motor system. For example, stopping the hand dampens the excitability of the task-irrelevant leg. However, it is unclear whether this ‘global suppression’ could apply across wider motor modalities. Here we tested whether stopping speech leads to suppression of the task-irrelevant hand. We used Transcranial Magnetic Stimulation over the primary motor cortex with concurrent electromyography from the hand. We found that when speech was successfully stopped the motor evoked potential from the task-irrelevant hand was significantly reduced compared to when the participant failed to stop speaking, or responded on non stop signal trials, or compared to baseline. This shows that when speech is quickly stopped, there is a broad suppression across the motor system. This has implications for the neural basis of speech control and stuttering.     

The cortical organization of lexical knowledge: a dual lexicon model of spoken language processing

Current accounts of spoken language assume the existence of a lexicon where wordforms are stored and interact during spoken language perception, understanding and production. Despite the theoretical importance of the wordform lexicon, the exact localization and function of the lexicon in the broader context of language use is not well understood. This review draws on evidence from aphasia, functional imaging, neuroanatomy, laboratory phonology and behavioral results to argue for the existence of parallel lexica that facilitate different processes in the dorsal and ventral speech pathways. The dorsal lexicon, localized in the inferior parietal region including the supramarginal gyrus, serves as an interface between phonetic and articulatory representations. The ventral lexicon, localized in the posterior superior temporal sulcus and middle temporal gyrus, serves as an interface between phonetic and semantic representations. In addition to their interface roles, the two lexica contribute to the robustness of speech processing.     

Processing prefixes and suffixes in handwriting production

Previous research showed that handwriting production is mediated by linguistically oriented processing units such as syllables and graphemes. The goal of this study was to investigate whether French adults also activate another kind of unit that is more related to semantics than phonology, namely morphemes. Experiment 1 revealed that letter duration and inter-letter intervals were longer for suffixed words than for pseudo-suffixed words. These results suggest that the handwriting production system chunks the letter components of the root and suffix into morpheme-sized units. Experiment 2 compared the production of prefixed and pseudo-prefixed words. The results did not yield significant differences. This asymmetry between suffix and prefix processing has also been observed in other linguistic tasks. In suffixed words, the suffix would be processed on-line during the production of the root, in an analytic fashion. Prefixed words, in contrast, seem to be processed without decomposition, as pseudo-affixed words.     

Perceiving onset clusters in infancy

By 9-months infants are sensitive to native-language sound combinations. Our studies show that while younger infants discriminate clusters, they are not sensitive to differences in statistical frequency. Thus, the emergence of phonotactic knowledge is driven by experience with the frequency of occurrence of the sound combinations in one's language.     

Anxiety and speaking in people who stutter: An investigation using the emotional Stroop task

People with anxiety disorders show an attentional bias towards threat or negative emotion words. This exploratory study examined whether people who stutter (PWS), who can be anxious when speaking, show similar bias and whether reactions to threat words also influence speech motor planning and execution. Comparisons were made between 31 PWS and 31 fluent controls in a modified emotional Stroop task where, depending on a visual cue, participants named the colour of threat and neutral words at either a normal or fast articulation rate. In a manual version of the same task participants pressed the corresponding colour button with either a long or short duration. PWS but not controls were slower to respond to threat words than neutral words, however, this emotionality effect was only evident for verbal responding. Emotionality did not interact with speech rate, but the size of the emotionality effect among PWS did correlate with frequency of stuttering. Results suggest PWS show an attentional bias to threat words similar to that found in people with anxiety disorder. In addition, this bias appears to be contingent on engaging the speech production system as a response modality. No evidence was found to indicate that emotional reactivity during the Stroop task constrains or destabilises, perhaps via arousal mechanisms, speech motor adjustment or execution for PWS.Educational objectives: The reader will be able to: (1) explain the importance of cognitive aspects of anxiety, such as attentional biases, in the possible cause and/or maintenance of anxiety in people who stutter, (2) explain how the emotional Stroop task can be used as a measure of attentional bias to threat information, and (3) evaluate the findings with respect to the relationship between attentional bias to threat information and speech production in people who stutter.     

Perfectionism and stuttering: Findings of an online survey

PurposeUsing a multi-dimensional measure of perfectionism: the Frost Multi-dimensional Perfectionism Scale (FMPS: Frost, Marten, Lahart, & Rosenblate, 1990), this study investigates: (a) whether adults who stutter (AWS) display more perfectionistic attitudes and beliefs than those who do not stutter, and (b) whether, in AWS, more perfectionistic attitudes and beliefs are associated with greater self-reported difficulty communicating verbally and speaking fluently.MethodIn the first analysis, FMPS responses from 81 AWS and 81 matched, normally-fluent controls were analyzed using logistic regression to investigate the relative contributions of four FMPS perfectionism-subscale self-ratings to the likelihood of being in the AWS group. In the subsequent analyses, data from the 81 AWS were analyzed using linear multiple regression to determine which FMPS subscale self-ratings best predicted their Communication-Difficulty and Fluency-Difficulty scores.ResultsBoth the likelihood of being a member of the AWS group, and also the magnitude of the AWS group's Communication-Difficulty and Fluency-Difficulty scores, were positively part-correlated to respondents’ Concern over Mistakes-Doubts about Actions (CMD) subscale self-ratings but negatively part-correlated to their Personal Standards (PS) subscale self-ratings.ConclusionsThe FMPS profiles of respondents who stutter suggest that, as a group, they are not abnormally perfectionistic overall, but may be (or perceive themselves to be) abnormally error-prone. Also, AWS who are more concerned about their errors and uncertain of their actions experience more difficulty communicating verbally and speaking fluently.Educational Objectives: After reading this article, participants will be able to: (a) describe the findings of previous research investigating the role of perfectionism in stuttering and psychopathologies; (b) discuss why a multidimensional assessment of perfectionism is important in relation to stuttering; (c) discuss ways in which data from perfectionism assessments can contribute to the planning of therapy for adults who stutter.     

Single-word predictions of upcoming language during comprehension: Evidence from the cumulative semantic interference task

Comprehenders predict upcoming speech and text on the basis of linguistic input. How many predictions do comprehenders make for an upcoming word? If a listener strongly expects to hear the word “sock”, is the word “shirt” partially expected as well, is it actively inhibited, or is it ignored? The present research addressed these questions by measuring the “downstream” effects of prediction on the processing of subsequently presented stimuli using the cumulative semantic interference paradigm. In three experiments, subjects named pictures (sock) that were presented either in isolation or after strongly constraining sentence frames (“After doing his laundry, Mark always seemed to be missing one …”). Naming sock slowed the subsequent naming of the picture shirt – the standard cumulative semantic interference effect. However, although picture naming was much faster after sentence frames, the interference effect was not modulated by the context (bare vs. sentence) in which either picture was presented. According to the only model of cumulative semantic interference that can account for such a pattern of data, this indicates that comprehenders pre-activated and maintained the pre-activation of best sentence completions (sock) but did not maintain the pre-activation of less likely completions (shirt). Thus, comprehenders predicted only the most probable completion for each sentence.     

Eye movements of monkey observers viewing vocalizing conspecifics

Primates, including humans, communicate using facial expressions, vocalizations and often a combination of the two modalities. For humans, such bimodal integration is best exemplified by speech-reading - humans readily use facial cues to enhance speech comprehension, particularly in noisy environments. Studies of the eye movement patterns of human speech-readers have revealed, unexpectedly, that they predominantly fixate on the eye region of the face as opposed to the mouth. Here, we tested the evolutionary basis for such a behavioral strategy by examining the eye movements of rhesus monkeys observers as they viewed vocalizing conspecifics. Under a variety of listening conditions, we found that rhesus monkeys predominantly focused on the eye region versus the mouth and that fixations on the mouth were tightly correlated with the onset of mouth movements. These eye movement patterns of rhesus monkeys are strikingly similar to those reported for humans observing the visual components of speech. The data therefore suggest that the sensorimotor strategies underlying bimodal speech perception may have a homologous counterpart in a closely related primate ancestor.