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Abstract
Purpose
To investigate links between sound discrimination and explicit sound-meaning mapping by preschoolers with and without developmental language disorder (DLD).
Method
We tested 26 children with DLD and 26 age- and gender-matched peers with typical language development (TLD). Inclusion was determined via results of standardised assessments of language and cognitive skills and a hearing screening. Children completed two computerised tasks designed to assess pitch and duration discrimination and explicit mapping of pitch- and duration-contrasting sounds to objects.
Result
Children with TLD more successfully mapped pitch categories to meanings than children with DLD. Children with TLD also showed significantly better overall sound discrimination than children with DLD. Sound-discrimination scores were marginally associated with overall sound-meaning mapping in multivariate analyses of covariance (MANCOVAs). Correlation tests indicated significant associations between discrimination and mapping, with moderate to large effect sizes. Thus, significant sound-discrimination differences between the groups may contribute to differences in sound-meaning-mapping accuracy.
Conclusion
Children with DLD had more difficulty mapping sound categories to meanings than TLD peers. We discuss possible explanations for this finding and implications for theoretical accounts of the aetiology of DLD.
Acknowledgements
The authors thank the children, parents, school directors, teachers, and speech-language pathologists who generously participated in and facilitated the research; LouAnn Gerken, Elena Plante, Andrew Lotto, Rebecca Gómez, and Sarah Creel for insightful suggestions about the conceptualisation of the study; Rebecca Vance, Lea Cuzner, and Molly Franz for assistance with participant recruitment; and the following student research assistants for helping conduct the study: Megan Figueroa, Jessie Erikson, Jamie Brown, Alexa Stevens, Jordan McGuire, Dominique Leon-Guerrero, Blaine Willcocks, Tauhida Zaman, Reem Anouti, Kalona Newcomb, Laura Mason, Kristen Ramos, Silvia Valdillez, Chelsea McGrath, Kirsten Davis, Megan Berry, Claire Small, Brandie Romanko, Karin Nystrom, Supreet Kaur, Sarah Elkinton, Roxana Magee, Ian Nool, Jill Martin, and Chia-Cheng Lee.
Disclosure statement
All authors have no financial or non-financial conflicts of interest to report.
Supplementary material
Supplemental data for this article can be accessed at https://doi.org/10.1080/17549507.2020.1750701
Notes
1 Voiced sounds like /b/ tend to be lower in pitch than voiceless sounds like /p/; vowels preceding voiced codas tend to be longer than those preceding voiceless codas.
2 This child was in the TLD group. Procedures were identical and relied on the same internal laboratory protocols and assessment procedures.
3 An Ear Scan 3 portable pure tone air conduction audiometer manufactured by Micro Audiometrics Corporation was used for hearing screenings.
4 In the model including Gender, there was a three-way interaction of Group, Gender, and Cue (Wilks’ Λ = 0.905, F(1,44) = 4.61, p = 0.037). To investigate the interaction, independent-samples t-tests compared the two Groups (TLD vs. DLD) separately for each combination of Gender and Cue. For boys (n = 38), children with TLD had higher pitch D′ scores (M = 2.64, SD = 1.76) than children with DLD (M = 1.02, SD = 2.00; t(36) = 2.66, p = 0.012). The two groups of boys did not significantly differ for duration. For girls (n = 14), by contrast, children with TLD showed significantly higher duration D′ scores (M = 2.58, SD = 1.27) than children with DLD (M = -0.32, SD = 2.45; t(12) = 2.77, p = 0.017). The two groups of girls did not significantly differ for pitch.
5 Additional analyses were conducted including the additional variables Age (in days), Maternal Education (in years), and Gender (M vs. F). There were no significant effects of (or interactions with) any of these additional variables, and the interaction of Group and Cue was not meaningfully affected by the inclusion of these other variables (F-values for the interaction were all above 4, and p-values ranged from 0.044-0.047). The interaction of Block and First Task was not meaningfully affected by the inclusion of Age or Maternal Education (F-values above 3.97, and p-values of 0.049 and 0.052). However, it was non-significant in the model that included Gender (F < 2, p > 0.2).
6 One aspect of the explicit-learning task used here that may have been challenging is the need to integrate visual feedback (smiley/frowny faces) to self-correct responses. Integrating feedback requires processing it visually, storing it in working memory, and using it to self-correct hypotheses about sound-object mappings. The memory component of integrating feedback could pose difficulty for children with DLD, given evidence of working-memory impairments (e.g. Leonard et al., Citation2007; note, however, that most findings of impaired working memory are in the verbal domain, not the visual domain; see Mainela-Arnold, Evans, & Coady, Citation2010, for discussion).
7 Future work using a similar discrimination task could also include contrasts in which both sounds are taken from the middle of the continuum, to promote generalisability.