Parent rating of intelligibility: A discussion of the construct validity of the Intelligibility in Context Scale (ICS) and normative data of the Swedish version of the ICS

Abstract

Background: Intelligibility can be defined as the speakers' ability to convey a message to the listener and it is considered the key functional measure of speech. The Intelligibility in Context Scale (ICS) is a parent rating scale used to assess intelligibility in children. Aims: To describe normative and validation data on the ICS in Swedish and to investigate how these are related to age, gender and multilingualism. Methods & Procedures: Two studies were included. Study 1 included ICS forms from 319 Swedish-speaking children (3:2-9:2 years:months). Study 2 included video recordings and ICS forms from 14 children with speech sound disorder (SSD) and two with typical speech. The video recordings were transcribed in the validation process, resulting in intelligibility reference scores to which ICS scores were correlated.Outcomes & Results: Study 1: The mean value of the ICS for the 319 children was 4.73. There were no differences in ICS score related to age or gender. The children in the multilingual group were significantly older than the monolingual group and had significantly lower ICS scores than the group of monolinguals. Study 2: There was a moderate correlation between the ICS score and the transcription-based intelligibility score, with the two children with typical speech excluded; however, this correlation was not significant. Conclusions & Implications:We contribute mean scores and percentiles on the ICS for Swedish-speaking children. The finding that the ICS does not provide valid measures of intelligibility for the included children with SSD suggests that the instrument measures a different construct.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Utility of the Intelligibility in Context Scale for Predicting Speech Intelligibility of Children with Cerebral Palsy

“…Transcription intelligibility scores are based on an isolated and focused exposure with a child’s speech, capturing objective details from specific speech samples in the absence of communicative context [ 7 , 14 ]. Our findings are similar to those of Sakash and colleagues [ 19 ] and Lagerberg and collaborators [ 30 ], who suggested that parent ratings of intelligibility and transcription intelligibility scores were correlated but were not equivalent measures. They advocated for the use of these two measures together when assessing speech intelligibility.…”

“…Composite ICS scores did not fall below 3 in the dataset, even for children with transcription intelligibility scores at or near 0%. Lagerberg and associates also reported a wide range of transcription intelligibility scores for ICS composite scores of 4 and below [ 30 ], which supports the notion that internal calibrations of parents regarding their child’s intelligibility as rated by the ICS may vary [ 19 ].…”

“…Across studies, results have shown correlations of varying strength between ICS composite scores and articulatory measures of speech (ranging from no correlation to moderate correlation) [ 24 , 25 , 26 , 27 , 28 ]. Lagerberg and colleagues suggested that the ICS, intended to be a measure of intelligibility, may be best compared to other measures of speech intelligibility, such as transcription intelligibility scores [ 30 ]. However, only two studies have examined the relationship between ICS scores and transcription intelligibility scores.…”

“…However, only two studies have examined the relationship between ICS scores and transcription intelligibility scores. These studies examined children with speech sound disorders (SSD) [ 30 ] and children with velopharyngeal insufficiency (VPI) [ 31 ]. Hosseinabad and associates noted a strong significant correlation between ICS scores and transcription intelligibility scores of children with VPI, indicating the potential clinical utility of the ICS as a proxy for objective measures.…”

Intelligibility in Context Scale: Growth Curves for Typically Developing English-Speaking Children Between Ages 2;6 and 9;11

“…Various methods have been developed to measure speech intelligibility, such as orthographic transcription, closed-set word identification, phonetic indices, and scaling methods. Previous literature has described the benefits and caveats of each method ( Kent et al, 1994 ; Lagerberg et al, 2021 ; Miller, 2013 ). Regardless of the method of measurement, age-based normative standards for the acquisition of intelligible speech in children are critically important to the identification of atypical performance.…”