The tone atlas of perceptual discriminability and perceptual distance: Four tone languages and five language groups

Available online 4 April 2022Some prior investigations suggest that tone perception is flexible, reasonably independent of native phonology, whereas others suggest it is constrained by native phonology. We address this issue in a systematic and comprehensive investigation of adult tone perception. Sampling from diverse tone and non-tone speaking communities, we tested discrimination of the three major tone systems (Cantonese, Thai, Mandarin) that dominate the tone perception literature, in relation to native language and language experience as well as stimulus variation (tone properties, presentation order, pitch cues) using linear mixed effect modelling and multidimensional scaling. There was an overall discrimination advantage for tone language speakers and for native tones. However, language- and tone-specific effects, and presentation order effects also emerged. Thus, over and above native phonology, stimulus variation exerts a powerful influence on tone discrimination. This study provides a tone atlas, a reference guide to inform empirical studies of tone sensitivity, both retrospectively and prospectively.Project conception (dB), and project management and data collection by the sixth author, BK, at the MARCS Institute for Brain, Behaviour and Development in Sydney Australia were supported by Australian Research Council Discovery Project grants (DP0988201, DP110105123) to the final author, dB. Data collection in Hong Kong was supported by Dr. Stanley Ho Medical Development Foundation. Data collection at the National University of Singapore was supported by an ODPRT grant for research excellence to LS. LL’s writing was supported by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 798658 hosted by Center for Multilingualism across the Lifespan at the University of Oslo, financed by Research Council of Norway through its Centers of Excellence funding scheme grant agreement No. 223265. MK’s writing was supported by the Basque Government through the BERC 2018-2021 program, by the Spanish Ministry of Science and Innovation through the Ramon y Cajal Research Fellowship, PID2019-105528GA-I00, and by the Spanish State Research Agency through BCBL Severo Ochoa excellence accreditation CEX2020-001010-S. We would like to thank Kay Wong for data collection in Hong Kong, Ms. Juthatip Duangmal and Ms. Nawasri Chonmahatrakul at MARCS-CILS NokHook BabyLab, Thammasat University for data collection in Thailand, Charlene Fu and Dilu Wewalaarachchi for data collection in Singapore; and Antonia Götz for discussions about analyses in R

Training Children to Perceive Non-native Lexical Tones: Tone Language Background, Bilingualism, and Auditory-Visual Information

This study investigates the role of language background and bilingual status in the perception of foreign lexical tones. Eight groups of participants, consisting of children of 6 and 8 years from one of four language background (tone or non-tone) × bilingual status (monolingual or bilingual)—Thai monolingual, English monolingual, English-Thai bilingual, and English-Arabic bilingual were trained to perceive the four Mandarin lexical tones. Half the children in each of these eight groups were given auditory-only (AO) training and half auditory-visual (AV) training. In each group Mandarin tone identification was tested before and after (pre- and post-) training with both auditory-only test (ao-test) and auditory-visual test (av test). The effect of training on Mandarin tone identification was minimal for 6-year-olds. On the other hand, 8-year-olds, particularly those with tone language experience showed greater pre- to post-training improvement, and this was best indexed by ao-test trials. Bilingual vs. monolingual background did not facilitate overall improvement due to training, but it did modulate the efficacy of the Training mode: for bilinguals both AO and AV training, and especially AO, resulted in performance gain; but for monolinguals training was most effective with AV stimuli. Again this effect was best indexed by ao-test trials. These results suggest that tone language experience, be it monolingual or bilingual, is a strong predictor of learning unfamiliar tones; that monolinguals learn best from AV training trials and bilinguals from AO training trials; and that there is no metalinguistic advantage due to bilingualism in learning to perceive lexical tones

Reading without spaces between words : eye movements in reading Thai

Studies of eye movements in reading alphabetic writing system languages, such as English, suggest that the optimal viewing position (OVP), the most effective target in each word that allows fastest word processing, is the word centre. In alphabetic languages with spaces between the words, research has shown that readers‟ preferred viewing location (PVL) is to the left of the OVP. It appears that spaces between words is the most salient low-level visual processing cue to guide the eyes during reading, for when the spaces are removed from the text of alphabetic spaced languages, reading rate decreases by approximately 35% and the PVL shifts dramatically from the word-centre towards the word-beginning. Although these finding are widely accepted, it is unclear how well such results generalize to languages without spaces between words – scriptio continua alphabetic languages. Thai is a good model of a scriptio continua language in which to investigate eye movements during reading, not only because it is written without spaces between words but because its orthography is also quite complicated in terms of visual information. In brief, characters such as vowels, tones, and other diacritics or even some parts of the consonants can be written above or below the main horizontal line. Reilly et al. (2003) surprisingly found that Thai adult readers also target the word centre during saccadic eye movements, even though there is no spacing to help indicate word boundaries. They suggested that the relative position-specific frequency of occurrence of final and initial characters serve as visual cues to guide eye movements of Thai readers. Analysis of the frequency of initial and final characters calculated for the texts used in their experiment confirm their suggestion that participants‟ landing site location tended to be closer to the word centre if the position-specific frequency of the initial and especially final characters are relatively high. The aim of this thesis was to test the effects of low-level visual distinctive features in Thai orthography – namely i) the relative frequency of occurrence of characters in the initial and final positions, and ii) spaces between words – on reading time, eye movement patterns and control, and fixation patterns of native Thai readers, both children and adults. Experiment 1 involved studies of reading time with a group of adults and four groups of children (1st, 2nd, 5th and 6th Graders, with half in each group being good and half being poor readers). This experiment focussed particularly on the start and end characters of words. It was found that relative frequency of occurrence of characters in the word-start and word-end positions had significant effects on reading time and reading accuracy of Thai participants across all ages. Higher frequency characters, especially word-start characters helped reduce reading time and spacing between words facilitated reading in general as indicated by shorter reading times, especially for poor reader young children. Differences due to groups and spacing decreased as the age of participants increased and their reading skills improved. Experiments 2 and 3 involved precise measurements of eye movements using the EyeLink II apparatus and followed up on the effects found in Experiment 1, those of position-specific frequency of word-start and word-end characters. In Experiment 2, adults of lower and higher education levels were tested on unspaced and spaced text reading either silently or aloud. It was found that Thai readers‟ PVL was at or near the word centre in all conditions. The presence or absence of spaces between words did not cause any dramatic changes to this PVL, like those found in the eye movements of English language readers presented with the unusual unspaced text. That is, for Thai readers reading normal unspaced text and unusual spaced text, the oculomotor patterns were the same in contrast to the dramatic change in English readers‟ eye movements when faced with the unusual unspaced text (Rayner et al., 1998). Nevertheless, in concert with the Experiment 1 reading time studies, spaces between words did allow faster reading in Thai readers; there were shorter first fixations and gaze durations for spaced than unspaced text. In addition, for reading aloud the PVL was closer to word start than for silent reading, and first fixation and gaze duration were longer for reading aloud. Relative frequency of characters especially at word-start position had significant effects on landing site location of Thai adults (skilled readers), i.e., higher start character frequency allowed participants to land their eyes at the PVL. Word-end character frequency had less effect on landing site but stronger effects on fixation time of the participants; both first fixation and gaze durations on words with higher end character frequency were shorter than those with the lower frequency. In Experiment 3, with two groups of children the results were similar although the landing site of the younger child participants was a bit further to the left of the word centre than it was for older children and adults, but still too far into the word to be designated as the word-initial area. Unlike the results of the adults‟ eye movements, spaces between words had significant effects on landing site location especially in younger children. Spaces facilitated young children’s oculomotor controls and assisted in lading their eyes closer to the OVP. There were no significant main effects of character frequency on landing site location of Thai children on the target words. However, frequency of characters in both word-start and word-end positions were used by younger child readers if there were no visible visual cue, i.e., spaces, available. Thus younger children relied on low-level visual information such as spaces between words more when reading. This may be because literacy teaching in Thai starts with spaced texts therefore younger children were more familiar with spaced text and try to use this information to locate word boundaries first before moving to the next resource such as the characters at word-start and word-end position. Generally the results of this thesis show that Thai readers, child and adult, use the same oculomotor controls when reading spaced and unspaced text. Adding spaces into the text does not change the PVL which remains near the OVP at or near word centre and similar to that of native readers of spaced alphabetic languages; however spacing does facilitate the landing site of younger children to be closer to the OVP. The developmental trend of eye movements in reading Thai seems to be that Thai readers rely less on visible visual cue as their reading skills increase at which point spaces between words facilitate reading time (first fixation and gaze duration) of skilled readers. Such results show that spaces between words are not essential for optimal eye movements in Thai. However, as spaces between words result in a decrease in reading time, spaces may aid in word recognition. These results have important implications for models of eye movements in reading which, at present, do not explicitly account for reading in scriptio continua languages. Additionally, two more reading time studies were conducted to investigate other distinctive features of Thai orthography (and details are given in Appendix C). In Experiment A, the focus was the feedback consistency versus inconsistency of initial and final characters. Similar results to Experiment 1 were found in terms of spacing conditions of the texts. Feedback inconsistent grapheme-phoneme relationships between letters and sounds slowed reading time for both initial and final consonants but there were more errors for final consonants, possibly due to significantly fewer final phonemes in the Thai phonological system. In Experiment B, the transparency of tone realisations was investigated. It was found that participants read words with transparent tone realisations faster and made fewer errors than for words with opaque tone realisations. Together these results show that reading time is sensitive to the influence of features of particular characters (frequency, grapheme-phoneme consistency, transparency of tone realisation) and also to spacing between words. Even though these features had some significant effects on reading time and reading accuracy of Thai readers, we still did not know if they would have any effects on eye movements of Thai readers or not. The results of these two additional reading time experiments provide the bases and hypotheses for further eye movement experiments; the effects found there need to be followed up in further studies. On the other hand the results of the reading time (Experiment 1) and eye movement (Experiment 2 and 3) studies of word-start and word-end character frequencies provided definitive evidence that the PVL in Thai, a scriptio continua language, is near the OVP at word centre as for spaces alphabetic languages. This finding should be further investigated in other scriptio continua languages such as Khmer (Cambodian) and Lao

Auditory-visual tone perception in hearing impaired Thai listeners

This study investigated the effects of hearing impairment and auditory vs. auditory-visual perceptions of lexical tone by native Thai hearing impaired listeners: Hearing Impaired with Hearing Aids (HI+HA), Hearing Impaired without Hearing Aids (HI-HA), and Normal Hearing (NH). Adults’ discrimination of the 5 Thai tones was investigated in the auditory-visual (AV), auditory-only (AO), and visual-only (VO) conditions. Generally, NH participants performed better than the two HI groups with hearing aids facilitating tone perception (HI+HA>HI-HA). The Falling-Rising (FR) pair of times was the easiest to discriminate for all three groups and there was a similar ranking of the relative discriminability of all 10 tone contrasts across groups. There was better tone discrimination in AV than in AO and both were much better than VO; and this was equally the case for all groups. The results show that Hearing Impaired individuals either with or without hearing aids can and do use visual speech information to augment auditory perception of tone, but do so in a similar, not a significantly more enhanced manner as the Normal Hearing individuals

The Lombard effect with Thai lexical tones : an acoustic analysis of articulatory modifications in noise

When in a noisy environment speakers modify their speech production by increasing loudness, vowel duration, and fundamental frequency (F0), a phenomenon known as Lombard speech. Here Lombard speech in Thai was investigated in order to determine the effects of noise on the realisation of F0 in Thai lexical tones. Analysis of the acoustic characteristics of the five Bangkok Thai tones, in both continuous speech and citation form, produced in noise and in quiet showed that F0 is heightened in Lombard compared with clear speech. In addition, generally the contour of the tones also changes in Lombard speech; contours tend to be exaggerated towards the end of the tone in a direction consistent with the contour of the tone

Auditory-visual discrimination and identification of lexical tone within and across tone languages

The aim of this research is to investigate the general features of lexical tones that might contribute to their categorisation. Thai tones were presented for (a) discrimination and (b) identification by native Thai and non-native Mandarin tone language participants in auditory-only (AO), visual-only (VO) and auditory-visual (AV) conditions. Discrimination tests revealed: (i) good auditory and auditory-visual discrimination of tone pairs by Thai and Mandarin perceivers, (ii) significant contribution of visual information to tone discrimination in Thai and Mandarin perceivers; (iii) greater AV>AO augmentation at 1500 vs 500 ms interstimulus interval (ISI), showing more use of visual information for tone at phonemic (tonemic) than phonetic (tonetic) levels; and (iv) better overall discrimination – and especially large AV>AO augmentation – of contour-contour than contour-level or level-level tone pairs. Identification tests showed, as expected, that Thai participants were accurate in identifying Thai tones, using both auditory and visual information. Mandarin participants were generally able to categorize the non-native Thai tones into their native tone categories, and also used visual information, especially for contour tones. The discrimination and identification data relationship is discussed as are implications for further studies

How to compare tones

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Towards an optimal tone space

The utility of tones spaces based on tone productions can be judged on the degree to which they (i) differentiate tone productions and (ii) predict tone perception. Here based on a production corpus, 5 different 2-dimensional tone spaces are constructed. Euclidean distances between tone pairs in these various tone spaces are then related to perceptual ability with tones by different language groups to determine relative tone space utility.1 page(s

Auditory-visual augmentation of Thai lexical tone perception in the elderly

This study investigated the effects of aging, auditory and auditory-visual perception of lexical tone of native Thai listeners. Elderly and younger Adults’ discrimination of the 5 Thai tones was investigated in audio-visual (AV), audio-only (AO), and visual-only (VO) conditions at two inter-stimulus intervals (ISIs) [500 and 1500 ms] in clear and noisy conditions. Generally, the Elderly performed more poorly than the Adults, but in both groups there was similar ranking of the relative discriminability of tone contrasts. Notably, in noise there was better tone discrimination in AV than in AO, and this was equally the case for young Adults and the Elderly. This shows that the elderly can and do use visual speech information to augment auditory perception of tone. The Elderly also benefitted more from the 1500 ms ISI suggesting that their tone perception is better when a more phonological (rather than acoustic) mode of processing is available

Cross-language categorisation of monosyllabic Thai tones by Mandarin and Vietnamese speakers : L1 phonological and phonetic influences

This study explores the influences of listeners’ native tone inventory on cross-language tone perception. Mandarin, Northern Vietnamese and Southern Vietnamese listeners (n = 13 per group; naive to Thai) categorised Thai tones into their native tone categories. Results show that all three groups categorised most Thai tones into their native tone categories. Their performance suggests that they attended to the phonetic details of the non-native tones, and that their assimilation patterns were influenced by the organisation of their native tone phonological systems as well as by the phonetic distances between native and non-native tones