Intelligibility in Context Scale: Normative and validation data for English- speaking preschoolers

Purpose: The purpose of this study was to describe normative and validation data on the Intelligibility in Context Scale (ICS; McLeod, Harrison, & McCormack, 2012c) for English-speaking children. Method: The ICS is a 7-item, parent-report measure of children's speech intelligibility with a range of communicative partners. Data were collected from the parents of 803 Australian English-speaking children ranging in age from 4;0 (years;months) to 5;5 (37.0% were multilingual). Results: The mean ICS score was 4.4 (SD = 0.7) out of a possible total score of 5. Children's speech was reported to be most intelligible to their parents, followed by their immediate family, friends, and teachers; children's speech was least intelligible to strangers. The ICS had high internal consistency (α = .94). Significant differences in scores were identified on the basis of sex and age but not on the basis of socioeconomic status or the number of languages spoken. There were significant differences in scores between children whose parents had concerns about their child's speech (M = 3.9) and those who did not (M = 4.6). A sensitivity of .82 and a specificity of .58 were established as the optimal cutoff. Test–retest reliability and criterion validity were established for 184 children with a speech sound disorder. There was a significant low correlation between the ICS mean score and percentage of phonemes correct (r = .30), percentage of consonants correct (r = .24), and percentage of vowels correct (r = .30) on the Diagnostic Evaluation of Articulation and Phonology (Dodd, Hua, Crosbie, Holm, & Ozanne, 2002). Thirty-one parents completed the ICS related to English and another language spoken by their child with a speech sound disorder. The significant correlations between the scores suggest that the ICS may be robust between languages. Conclusions: This article provides normative ICS data for English-speaking children and additional validation of the psychometric properties of the ICS. The robustness of the ICS was suggested because mean ICS scores were not affected by socioeconomic status, number of languages spoken, or whether the ICS was completed in relation to English or another language. The ICS is recommended as a screening measure of children's speech intelligibility.