Validation of the Intelligibility in Context Scale for Jamaican Creole-speaking preschoolers

Purpose: To describe validation of the Intelligibility in Context Scale (ICS; McLeod et al.,2012a) and ICS-Jamaican Creole (ICS-JC; McLeod et al., 2012b; Washington & Devonish Trans.) in a sample of typically-developing 3-to-6-year-old Jamaicans. Method : One-hundred and forty-five preschooler–parent dyads participated in the study. Parents completed the 7-item ICS (n = 145) and ICS-JC (n = 98) to rate children's speech intelligibility (5-point scale) across communication partners (parents, immediate family, extended family, friends, acquaintances, strangers). Preschoolers completed the Diagnostic Evaluation of Articulation and Phonology (DEAP; Dodd, Hua, Crosbie, Holm, & Ozanne, 2006) in English and Jamaican Creole to establish speech-sound competency. For this sample, we examined validity and reliability (interrater, test–rest, internal consistency) evidence using measures of speech-sound production: (a) percentage of consonants correct, (b) percentage of vowels correct, and (c) percentage of phonemes correct. Result: ICS and ICS-JC ratings showed preschoolers were always (5) to usually (4) understood across communication partners (ICS, M = 4.43; ICS-JC, M = 4.50). Both tools demonstrated excellent internal consistency (α = .91), high interrater, and test-retest reliability. Significant correlations between the two tools and between each measure and language-specific percentage of consonants correct, percentage of vowels correct, and percentage of phonemes correct provided criterion-validity evidence. A positive correlation between the ICS and age further strengthened validity evidence for that measure.
Conclusions: Both tools show promising evidence of reliability and validity in describing functional speech intelligibility for this group of typically developing Jamaican preschoolers.