On the locus of individual differences in perceptual flexibility: ERP evidence for perceptual warping of speech sounds

Listeners vary in how they categorize speech sounds: some are more step-like, while others are more gradient. Recent work suggests that gradient listeners are more flexible in cue integration and recovery from misperceptions (Kapnoula et al., 2017, 2021). We investigated the source of these differences and asked how they cascade to lexical processing. Individual differences in speech categorization were assessed via a visual analogue scaling (VAS) task. Following Toscano et al. (2010), we used the N1 ERP component to track pre-categorical encoding of speech cues. Separate tasks were used to measure inhibitory control and lexical processes. The N1 linearly tracked the continuum, reflecting a fundamentally gradient speechperception; however, for step-like listeners this linearity was disrupted near the boundary. This suggests that, while all listeners are generally gradient, there are individual differences deriving from the idiosyncratic encoding of specific cues, and that cue-level gradiency cascadesthroughout the system.

Gradient activation of speech categories facilitates listeners’ recovery from lexical garden paths, but not perception of speech-in-noise

Listeners activate speech sound categories in a gradient way and this information is maintained and affects activation of items at higher levels of processing (McMurray et al., 2002; Toscano et al., 2010). Recent findings by Kapnoula, Winn, Kong, Edwards, and McMurray (2017) suggest that the degree to which listeners maintain within-category information varies across individuals. Here we assessed the consequences of this gradiency for speech perception. To test this, we collected a measure of gradiency for different listeners using the visual analogue scaling (VAS) task used by Kapnoula et al. (2017). We also collected two independent measures of performance in speech perception: a visual world paradigm (VWP) task measuring participants’ ability to recover from lexical garden paths (McMurray et al., 2009) and a speech perception task measuring participants’ perception of isolated words in noise. Our results show that categorization gradiency does not predict participants’ performance in the speech-in-noise task. However, higher gradiency predicted higher likelihood of recovery from temporarily misleading information presented in the VWP task. These results suggest that gradient activation of speech sound categories is helpful when listeners need to reconsider their initial interpretation of the input, making them more efficient in recovering from errors.

Perceptual Judgments of Resonance, Nasal Airflow, Understandability, and Acceptability in Speakers with Cleft Palate: Ordinal versus Visual Analogue Scaling

Objective To investigate the reliability of ordinal versus visual analogue scaling (VAS) ratings for perceptual judgments of nasal resonance, nasal airflow, understandability, and acceptability in speakers with cleft palate. Design Within-subjects comparative study. Setting Multisite. Participants Five specialist speech and language therapists from U.K. Regional Cleft Centres. Outcome Measures Participants rated 30 audio speech samples obtained from the Speech and Language Therapy archives of Great Ormond Street Hospital. They rated the identified speech parameters using each scaling method, with 1 month between rating tasks. The model of best fit was determined to examine validity, and both intra- and inter-rater reliability were also computed. Results VAS ratings were valid for all parameters when plotted against ordinal ratings, and the model of best fit revealed only a slightly stronger curvilinear than linear relationship between the scaling methods. Intra-rater reliability was high for both rating methods across all six speech parameters. There was also high inter-rater reliability for both ordinal and VAS ratings of hypernasality, nasal emission, nasal turbulence, understandability, and acceptability, and for the ordinal ratings of hyponasality. Conclusions Perceptual judgments of nasal resonance, nasal airflow, understandability, and acceptability were similar using VAS and ordinal scaling, indicating that both scaling methods were appropriate for measuring the cleft speech parameters. VAS, however, may offer statistical advantages, and there is a growing body of evidence advocating its use for the measurement of prothetic speech parameters.

Comparison between Continuous and Discrete Measurements of Breathlessness during Exercise in Normal Subjects Using a Visual Analogue Scale

1. Visual analogue scaling of breathlessness made at discrete intervals during ventilatory stimulation tests can provide useful information about the intensity of this sensation. The aim of the present study was to investigate the use of continuous visual analogue scaling as a means of improving the temporal resolution of this measurement. 2. Six normal naive subjects scaled breathlessness using a visual analogue scale, during steady-state exercise. Further changes in this sensation were induced by either sustained hypercapnia or acute hypoxia; these responses were assessed either continuously or at discrete 30 s intervals and the two scaling methods were compared. 3. The continuous method of assessing breathlessness compared favourably with that of the more established discrete method, providing reproducible measurements in repeated tests equivalent in intensity to those obtained every 30 s. 4. Transient changes in the sensation of breathlessness produced by acute episodes of hypoxia were identified using the continuous scaling method but not with discrete scaling. 5. The continuous method of scaling breathlessness should aid the investigation of the neurophysiological basis of this sensation by allowing temporal relationships between changes in respiratory variables and the sensory consequences to be more carefully defined.

Effects of naloxone on the sensation of dyspnea during acute respiratory stress in normal adults

To clarify whether endogenous opioids modulate the dyspnea intensity and, if so, by what mechanism they act on it, we examined 12 healthy male volunteers aged 19–27 yr for ventilatory and peak mouth pressure (Pm) responses to hypoxic progressive hypercapnia with inspiratory flow-resistive loading after the intravenous infusion of 3 mg of naloxone or saline. The intensity of dyspnea was simultaneously assessed by visual analogue scaling every 15 s. Naloxone administration increased both ventilatory and Pm responses to hypoxic progressive hypercapnia (P < 0.05 for both). The increase in dyspnea intensity for a given increase in end-tidal PCO2 was significantly greater after naloxone infusion than after saline (P < 0.05). However, there were no differences in the increase in dyspnea intensity for a given increase in minute ventilation or Pm. These results suggest that the endogenous opioid system suppresses the respiratory output under a strong, acute respiratory stress in normal adults and that this system may relieve the dyspnea sensation secondary to the suppression of the brain stem respiratory center without specific effects on the processing of respiratory sensations in the higher brain.

The measurement of breathlessness induced in normal subjects: individual differences

1. Normal subjects show wide variability in their sensory scaling of breathlessness for equivalent degrees of ventilatory stimulation and behave ‘characteristically’ irrespective of stimulus type. 2. Observed differences are not explained by physical characteristics, ventilatory sensitivity or pattern of breathing although there is a weak association with the degree of physical fitness. 3. Differences are seen when scaling is performed with reference to both rigidly defined extremes of breathlessness (visual analogue scaling) and a subject's own relative changes in the intensity of this sensation (magnitude estimation). 4. These findings may explain the common observation, in patients with respiratory disease, of dyspnoea out of proportion to the pathophysiological state.

The Measurement of Breathlessness Induced in Normal Subjects: Validity of two Scaling Techniques

1. The intensity of breathlessness induced by ventilatory stimulation resulting from hypercapnia, hypoxia or exercise has been quantified in normals by using the two different sensory scaling techniques of linear visual analogue scaling and ratio magnitude estimation. 2. In naive individuals both techniques show good face validity. 3. When related to ventilation, quantification of breathlessness is moderately reproducible with both methods, even when subjects are kept in ignorance of the pattern of ventilatory stimulation. 4. There is a small within- and large between-subject variability with both scaling techniques; possible factors responsible are discussed. 5. The reproducibility of visual analogue scaling when related to ventilation is independent of the nature of the ventilatory stimulus and is maintained over intervals as long as 1 week when memory for the score given is unlikely to be an important factor. 6. The difficulties of interpreting subjective estimates of perceived breathlessness are discussed, together with the relative merits of the two scaling techniques.