Response to Letter to the Editor: Do Pediatric Cochlear Implant Recipients Display Domain-General Sequencing Difficulties? A Comment on Davidson et al. (2019).

<zdoi; 10.1097/AUD.0000000000000881> 1055 0196/0202/2020/414-1055/0 • Ear & Hearing • Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved • Printed in the U.S.A. To the Editor: We appreciate the opportunity to respond to Conway et al. regarding their interpretation of the data from our 2019 working memory article entitled “Effects of early auditory deprivation on working memory and reasoning abilities in verbal and visuospatial domains for pediatric cochlear implant recipients. ” In their letter to the editor, these colleagues contend that the overall conclusions from our article are not completely accurate and require a more nuanced interpretation. Specifically, they report that the following conclusions are not supported by our published data: “the results of this study suggest that working memory deficits in children with CIs are domain specific” (Davidson et al. 2019, page 523). and “overall, the children with CIs scored significantly lower on both simple and complex verbal working memory tasks compared with their age mates with NH; however, their performance on measures of visuospatial working memory tasks was similar to NH peers” (Davidson et al. 2019, page 525). Alternatively, Conway et al. conclude “We believe the most appropriate conclusion is that children with CIs exhibited lower performance across all four working memory tasks, regardless of domain or task complexity. ” They suggest that the underlying issues with our interpretation of the data are two-fold: (1) Absence of a statistically significant interaction in the analysis of covariance (ANCOVA) results between domain (verbal versus visuospatial working memory) and group (cochlear implant [CI] versus normal-hearing [NH] groups) indicates that the CI group scored below NH in both domains. (2) Our interpretation that overlapping confidence intervals (95% confidence intervals) suggest that the CI and NH group performance is similar for visuospatial working memory tasks is not supported. The overall goal of our study was to compare verbal and visuospatial working memory in children with NH and with CIs. Based on several articles that discuss the challenges and limitations of null hypothesis statistical tests, we presented both null hypothesis statistical tests and confidence intervals (Coulson et al. 2010; Cumming 2014; Oleson et al. 2019). As stated in the article, after entering age and maternal education as covariates in the ANCOVA, a significant main effect was found for group (CI versus NH), but no significant interactions for group and domain (verbal versus visual-spatial) or complexity (simple versus complex). We also report ANCOVA models when comparing the CI and NH group performance on two reasoning tasks from the Wechsler Intelligance Scale for Children -V (WISC-V): Picture Concepts (verbally mediated) and Matrix Reasoning (visuospatial) and a vocabulary test (Peabody Picture Vocabulary Test [PPVT]). Statistically significant group effects were found for WISC Picture Concepts and PPVT, but not for WISC Matrix Reasoning. We also plotted the covariate-adjusted z scores with 95% confidence intervals on all tasks including working memory, vocabulary, and reasoning. We felt that it was important to note the apparent differences in overlap of the mean scores with 95% confidence intervals for verbal and visual-spatial tasks, and we felt that it was important to share these distributions with the reader. The lack of overlap of the confidence intervals for CI and NH groups in performance on the verbal working memory tasks, the PPVT vocabulary test, and to some degree, the Picture Concepts portion of the WISC supports our conclusion that these children with CIs exhibit deficits in verbal skills compared with their age mates with NH. The statistically significant differences from the ANCOVA along with effect sizes (Cohens d) of 1.58 and 0.43 reported for the PPVT and the Picture Concepts subtest, respectively, are congruent with the confidence interval data. As reported by Conway et al, the effect size (Cohens d) values of 0.25 and 0.29 for group differences on visuospatial simple and complex working memory tasks, respectively, are smaller in magnitude compared with the effect sizes for the simple and complex verbal working memory tasks (d = 0.75 and 0.60, respectively). The effect size for the Matrix Reasoning portion of the WISC is even smaller (d = 0.18). Nevertheless, our conclusion that the CI group performance on visuospatial working memory tasks was on par with NH age mates, based on overlapping confidence intervals and relatively small effect sizes, is not warranted. To further explore the alternative hypothesis of no difference between CI and NH groups, we recently followed up the standard analysis of variance with a Bayesian analysis (Lakens et al. 2018; Brydges & Gaeta 2019). This duplicates the results of the analysis of variance in its estimates of effects but more importantly allows derivation of Bayes Factors. The group main effect is clearly present in the data; the group interactions are not. Using prior distributions that assume a normal distribution with an SD of 2.5 for the linear model coefficients, the Bayes Factors for the group main effect is 7.0 compared with a model that excludes the group main effect. The Bayes Factor is 458.4 for a model that excludes the interactions involving group compared with a model that includes those interactions. In other words, given the data, the model that does not include group interactions (including the group × domain interaction) is 458 times more likely than a model that includes the group interactions. Letter to the Editor