Varghese Peter | Western Sydney University (original) (raw)

Papers by Varghese Peter

The human ability to comprehend speech regardless of variation across speakers and accents has lo... more The human ability to comprehend speech regardless of variation across speakers and accents has long puzzled researchers. Human listeners appear to employ separate mechanisms to cope with speaker versus accent variation. The present study uses event-related potentials (ERP) to test whether such different mechanisms exist at a pre-attentive level of speech processing. We assessed Australian English monolinguals' and bilinguals' perceptual sensitivity to four types of variation in vowels: namely, variation in speaker identity, gender, accent, and vowel category. Interestingly, listeners showed similar results regardless of their linguistic background. As expected, listeners showed large sensitivity to accent changes. Rather surprisingly, however, they were more sensitive to changes in speaker gender than to changes in vowel category. These results are not in line with those of overt vowel classification but are explained by adults' sensitivity to large differences in voice ...

Acoustic properties of vowels differ across speakers and dialects. § It is unclear whether in pe... more Acoustic properties of vowels differ across speakers and dialects. § It is unclear whether in perception, speaker and dialect variation are handled (i.e. normalized) in the same way. § Speaker normalization seems to occur automatically, without lexical knowledge, even in non-­‐ human animals such as chinchillas and zebra finches [1,4]. => Speaker normalization might be a general auditory process. § Dialect normalization seems to require lexical knowledge [2,3]. => Dialect normalization might be a learned linguistic process.

BMC neuroscience, Jan 26, 2014

BackgroundThe closure positive shift (CPS) event related potential (ERP) is commonly used as a ne... more BackgroundThe closure positive shift (CPS) event related potential (ERP) is commonly used as a neural measure of phrase boundary perception in speech. The present study investigated whether the CPS was elicited by acoustic cues at phrase boundaries in English. ERPs were recorded when participants listened passively to sentences with either early or late phrase boundaries.ResultsThe closure positive shift (CPS) ERP was elicited at both early and late phrase boundaries. However, the latency, amplitude, and scalp distribution of these passive CPS ERPs in English sentences differed to active CPS ERPs measured in non-English sentences in previous studies.ConclusionsThese results show that acoustic cues at the phrase boundaries in English are sufficient to elicit the CPS, and suggest that different processes might be involved in the generation of the CPS in active and passive conditions.

NeuroReport, 2013

Young adults with no history of hearing concerns were tested to investigate their /da/-evoked cor... more Young adults with no history of hearing concerns were tested to investigate their /da/-evoked cortical auditory evoked potentials (P1-N1-P2) recorded from 32 scalp electrodes in the presence and absence of noise at three different loudness levels (soft, comfortable, and loud), at a fixed signal-to-noise ratio (+3 dB). P1 peak latency significantly increased at soft and loud levels, and N1 and P2 latencies increased at all three levels in the presence of noise, compared with the quiet condition. P1 amplitude was significantly larger in quiet than in noise conditions at the loudest level. N1 amplitude was larger in quiet than in noise for the soft level only. P2 amplitude was reduced in the presence of noise to a similar degree at all loudness levels. The differential effects of noise on P1, N1, and P2 suggest differences in auditory processes underlying these peaks. The combination of level and signal-to-noise ratio should be considered when using cortical auditory evoked potentials as an electrophysiological indicator of degraded speech processing.

Journal of the American Academy of Audiology, 2014

Background: There are many clinically available tests for the assessment of auditory processing s... more Background: There are many clinically available tests for the assessment of auditory processing skills in children and adults. However, there is limited data available on the maturational effects on the performance on these tests.

Quarterly Journal of Experimental Psychology, 2012

In two experiments, we examined the effect of intensity and intensity change on judgements of pit... more In two experiments, we examined the effect of intensity and intensity change on judgements of pitch differences or interval size. In Experiment 1, 39 musically untrained participants rated the size of the interval spanned by two pitches within individual gliding tones. Tones were presented at high intensity, low intensity, looming intensity (up-ramp), and fading intensity (down-ramp) and glided between two pitches spanning either 6 or 7 semitones (a tritone or a perfect fifth interval). The pitch shift occurred in either ascending or descending directions. Experiment 2 repeated the conditions of Experiment 1 but the shifts in pitch and intensity occurred across two discrete tones (i.e., a melodic interval). Results indicated that participants were sensitive to the differences in interval size presented: Ratings were significantly higher when two pitches differed by 7 semitones than when they differed by 6 semitones. However, ratings were also dependent on whether the interval was high or low in intensity, whether it increased or decreased in intensity across the two pitches, and whether the interval was ascending or descending in pitch. Such influences illustrate that the perception of pitch relations does not always adhere to a logarithmic function as implied by their musical labels, but that identical intervals are perceived as substantially different in size depending on other attributes of the sound source.

Abstract The aim of this study was to determine if duration-related stress in speech and music is... more Abstract The aim of this study was to determine if duration-related stress in speech and music is processed in a similar way in the brain. To this end, we tested 20 adults for their abstract mismatch negativity (MMN) event-related potentials to two duration-related stress patterns: stress on the first syllable or note (long-short), and stress on the second syllable or note (short-long). A significant MMN was elicited for both speech and music except for the short-long speech stimulus.

Neuroscience letters, Jan 1, 2010

2017 by Varghese Peter

Brain & Language, 2017

Speech sound acoustic properties vary largely across speakers and accents. When perceiving speech... more Speech sound acoustic properties vary largely across speakers and accents. When perceiving speech, adult listeners normally disregard non-linguistic variation caused by speaker or accent differences, in order to comprehend the linguistic message, e.g. to correctly identify a speech sound or a word. Here we tested whether the process of normalizing speaker and accent differences, facilitating the recognition of linguistic information, is found at the level of neural processing, and whether it is modulated by the listeners' native language. In a multi-deviant oddball paradigm, native and nonnative speakers of Dutch were exposed to naturally-produced Dutch vowels varying in speaker, sex, accent, and phoneme identity. Unexpectedly, the analysis of mismatch negativity (MMN) amplitudes elicited by each type of change shows a large degree of early perceptual sensitivity to non-linguistic cues. This finding on perception of naturally-produced stimuli contrasts with previous studies examining the perception of synthetic stimuli wherein adult listeners automatically disregard acoustic cues to speaker identity. The present finding bears relevance to speech normalization theories, suggesting that at an unattended level of processing , listeners are indeed sensitive to changes in fundamental frequency in natural speech tokens.

The human ability to comprehend speech regardless of variation across speakers and accents has lo... more The human ability to comprehend speech regardless of variation across speakers and accents has long puzzled researchers. Human listeners appear to employ separate mechanisms to cope with speaker versus accent variation. The present study uses event-related potentials (ERP) to test whether such different mechanisms exist at a pre-attentive level of speech processing. We assessed Australian English monolinguals' and bilinguals' perceptual sensitivity to four types of variation in vowels: namely, variation in speaker identity, gender, accent, and vowel category. Interestingly, listeners showed similar results regardless of their linguistic background. As expected, listeners showed large sensitivity to accent changes. Rather surprisingly, however, they were more sensitive to changes in speaker gender than to changes in vowel category. These results are not in line with those of overt vowel classification but are explained by adults' sensitivity to large differences in voice ...

Acoustic properties of vowels differ across speakers and dialects. § It is unclear whether in pe... more Acoustic properties of vowels differ across speakers and dialects. § It is unclear whether in perception, speaker and dialect variation are handled (i.e. normalized) in the same way. § Speaker normalization seems to occur automatically, without lexical knowledge, even in non-­‐ human animals such as chinchillas and zebra finches [1,4]. => Speaker normalization might be a general auditory process. § Dialect normalization seems to require lexical knowledge [2,3]. => Dialect normalization might be a learned linguistic process.

BMC neuroscience, Jan 26, 2014

BackgroundThe closure positive shift (CPS) event related potential (ERP) is commonly used as a ne... more BackgroundThe closure positive shift (CPS) event related potential (ERP) is commonly used as a neural measure of phrase boundary perception in speech. The present study investigated whether the CPS was elicited by acoustic cues at phrase boundaries in English. ERPs were recorded when participants listened passively to sentences with either early or late phrase boundaries.ResultsThe closure positive shift (CPS) ERP was elicited at both early and late phrase boundaries. However, the latency, amplitude, and scalp distribution of these passive CPS ERPs in English sentences differed to active CPS ERPs measured in non-English sentences in previous studies.ConclusionsThese results show that acoustic cues at the phrase boundaries in English are sufficient to elicit the CPS, and suggest that different processes might be involved in the generation of the CPS in active and passive conditions.

NeuroReport, 2013

Young adults with no history of hearing concerns were tested to investigate their /da/-evoked cor... more Young adults with no history of hearing concerns were tested to investigate their /da/-evoked cortical auditory evoked potentials (P1-N1-P2) recorded from 32 scalp electrodes in the presence and absence of noise at three different loudness levels (soft, comfortable, and loud), at a fixed signal-to-noise ratio (+3 dB). P1 peak latency significantly increased at soft and loud levels, and N1 and P2 latencies increased at all three levels in the presence of noise, compared with the quiet condition. P1 amplitude was significantly larger in quiet than in noise conditions at the loudest level. N1 amplitude was larger in quiet than in noise for the soft level only. P2 amplitude was reduced in the presence of noise to a similar degree at all loudness levels. The differential effects of noise on P1, N1, and P2 suggest differences in auditory processes underlying these peaks. The combination of level and signal-to-noise ratio should be considered when using cortical auditory evoked potentials as an electrophysiological indicator of degraded speech processing.

Journal of the American Academy of Audiology, 2014

Background: There are many clinically available tests for the assessment of auditory processing s... more Background: There are many clinically available tests for the assessment of auditory processing skills in children and adults. However, there is limited data available on the maturational effects on the performance on these tests.

Quarterly Journal of Experimental Psychology, 2012

In two experiments, we examined the effect of intensity and intensity change on judgements of pit... more In two experiments, we examined the effect of intensity and intensity change on judgements of pitch differences or interval size. In Experiment 1, 39 musically untrained participants rated the size of the interval spanned by two pitches within individual gliding tones. Tones were presented at high intensity, low intensity, looming intensity (up-ramp), and fading intensity (down-ramp) and glided between two pitches spanning either 6 or 7 semitones (a tritone or a perfect fifth interval). The pitch shift occurred in either ascending or descending directions. Experiment 2 repeated the conditions of Experiment 1 but the shifts in pitch and intensity occurred across two discrete tones (i.e., a melodic interval). Results indicated that participants were sensitive to the differences in interval size presented: Ratings were significantly higher when two pitches differed by 7 semitones than when they differed by 6 semitones. However, ratings were also dependent on whether the interval was high or low in intensity, whether it increased or decreased in intensity across the two pitches, and whether the interval was ascending or descending in pitch. Such influences illustrate that the perception of pitch relations does not always adhere to a logarithmic function as implied by their musical labels, but that identical intervals are perceived as substantially different in size depending on other attributes of the sound source.

Abstract The aim of this study was to determine if duration-related stress in speech and music is... more Abstract The aim of this study was to determine if duration-related stress in speech and music is processed in a similar way in the brain. To this end, we tested 20 adults for their abstract mismatch negativity (MMN) event-related potentials to two duration-related stress patterns: stress on the first syllable or note (long-short), and stress on the second syllable or note (short-long). A significant MMN was elicited for both speech and music except for the short-long speech stimulus.

Neuroscience letters, Jan 1, 2010

Brain & Language, 2017

Speech sound acoustic properties vary largely across speakers and accents. When perceiving speech... more Speech sound acoustic properties vary largely across speakers and accents. When perceiving speech, adult listeners normally disregard non-linguistic variation caused by speaker or accent differences, in order to comprehend the linguistic message, e.g. to correctly identify a speech sound or a word. Here we tested whether the process of normalizing speaker and accent differences, facilitating the recognition of linguistic information, is found at the level of neural processing, and whether it is modulated by the listeners' native language. In a multi-deviant oddball paradigm, native and nonnative speakers of Dutch were exposed to naturally-produced Dutch vowels varying in speaker, sex, accent, and phoneme identity. Unexpectedly, the analysis of mismatch negativity (MMN) amplitudes elicited by each type of change shows a large degree of early perceptual sensitivity to non-linguistic cues. This finding on perception of naturally-produced stimuli contrasts with previous studies examining the perception of synthetic stimuli wherein adult listeners automatically disregard acoustic cues to speaker identity. The present finding bears relevance to speech normalization theories, suggesting that at an unattended level of processing , listeners are indeed sensitive to changes in fundamental frequency in natural speech tokens.