Lexical tone perception by CI users (Holt et al., 2018)

Purpose: The purpose of this study is to assess Cantonese word recognition and the discrimination of Cantonese tones with manipulated contours by child and adolescent cochlear implant (CI) users and a group of peers with normal hearing (NH). It was hypothesized that the CI users would perform more poorly than their counterparts with NH in both tasks and that CI users implanted before 2 years of age would perform better than those implanted after 2 years.Method: Forty-one participants were recruited from hospitals, schools, and kindergartens in Hong Kong: Ten CI users implanted at or before 2 years of age (“early” CI group), 13 CI users implanted after 2 years of age (“late” CI group), and 18 individuals with NH. The mean age at implantation of the early CI group was 1.5 years (SD = 0.3), and for the late CI group, it was 4.3 years (SD = 2.1). Participants were a mean of 13.3 years of age (SD = 3.7) at time of testing. Participants completed a Cantonese word recognition test and a discrimination task using Cantonese tones with modified fundamental frequency trajectories.Results: Both CI user groups obtained significantly lower scores than the group with NH on the word recognition test. Mean percent correct scores for the word recognition test were 79% for the early CI group, 69% for the late CI group, and 97% for the group with NH. The group with NH consistently achieved higher scores than the CI user groups when discriminating manipulated Cantonese tones. Increasing the acoustic difference between tones improved discrimination performance for CI users for level tone contrasts only. CI users implanted at or before 2 years of age obtained higher scores than those implanted later.Conclusions: The results of this study add further evidence that children using CIs do not perform as well as peers in perceiving Cantonese tones. Modification of tones to increase pitch range did not consistently improve the ability of children with implants to perceive the difference between tones. Further research is required to fully assess potential benefits of early implantation for speakers of tonal languages.Cantonese has six phonologically distinct tones (Yip, 2002). The Cantonese tone system includes three tones uttered with a relatively stable F0 but which differ in relative F0 level (also referred to as F0 height). These are the high (T1), mid (T3), and low (T6) static tones. T2, T4, and T5 are dynamic tones, whose F0 trajectory changes over the duration of the word.Supplemental Material S1. T1 and its manipulations.Supplemental Material S2. T2 and its manipulations compared to T5.Supplemental Material S3. T2 and its manipulations compared to T4.Supplemental Material S4. T4 and its manipulations compared to T6.Holt, C. M., Lee, K. Y. S., Dowell, R. C., & Vogel, A. P. (2018). Perception of Cantonese lexical tones by pediatric cochlear implant users. Journal of Speech, Language, and Hearing Research, 61, 174–185. https://doi.org/10.1044/2017_JSLHR-H-17-0027研究目的：本研究旨在评估儿童及青少年人工耳蜗（cochlear implant, CI）使用者与同龄正常听力（normal hearing, NH）被试对粤语词汇的识别能力，以及对轮廓经过调控的粤语声调的辨别能力。本研究提出如下假设：CI使用者在两项任务中的表现均劣于NH组被试；且2岁前接受人工耳蜗植入的CI使用者表现优于2岁后植入者。 研究方法：本研究从中国香港的医院、中小学及幼儿园招募了41名被试：包括10名2岁及之前接受人工耳蜗植入的CI使用者（「早植入CI组」）、13名2岁后接受植入的CI使用者（「晚植入CI组」），以及18名正常听力个体。早植入CI组的平均植入年龄为1.5岁（标准差SD=0.3），晚植入CI组的平均植入年龄为4.3岁（SD=2.1）。所有被试在测试时的平均年龄为13.3岁（SD=3.7）。所有被试均完成了粤语词汇识别测试，以及使用基频（fundamental frequency, F0）轨迹经过修改的粤语声调的辨别任务。 研究结果：在词汇识别测试中，两个CI组的得分均显著低于NH组。词汇识别测试的平均正确率分别为：早植入CI组79%、晚植入CI组69%、NH组97%。在辨别经过调控的粤语声调任务中，NH组的得分始终高于两个CI组。仅在平调对比任务中，增大声调间的声学差异可提升CI使用者的辨别表现。2岁及之前接受植入的CI使用者得分高于晚植入者。 研究结论：本研究结果进一步证实，人工耳蜗植入儿童在感知粤语声调方面的表现不及同龄正常听力个体。通过调整声调以扩大音高范围的操作，并未持续提升植入儿童对声调差异的感知能力。未来仍需开展进一步研究，以全面评估早期植入对声调语言使用者的潜在益处。 粤语共有6个具有音系差异的声调（Yip, 2002）。粤语声调系统包含3个基频（F0）相对稳定，但相对F0水平（亦称为F0高度）存在差异的平调，分别为高调（T1）、中调（T3）与低调（T6）。T2、T4与T5为动态声调，其基频轨迹会在音节持续时长内发生变化。 补充材料S1：T1及其调控变体 补充材料S2：T2及其与T5的对比调控变体 补充材料S3：T2及其与T4的对比调控变体 补充材料S4：T4及其与T6的对比调控变体 参考文献：Holt, C. M., Lee, K. Y. S., Dowell, R. C., & Vogel, A. P. (2018). 儿童人工耳蜗使用者对粤语词汇声调的感知. *《言语、语言与听力研究期刊》*, 61卷, 174–185页. https://doi.org/10.1044/2017_JSLHR-H-17-0027