Normative data and construct validity of a cross-linguistic functional speech outcome, the Intelligibility in Context Scale: Italian (ICS-I)

Abstract

Objectives: The Intelligibility in Context Scale (ICS) is a parent-report scale, world-wide translated and widely validated, by which parents can rate their child's functional speech intelligibility according to seven different communicative partners. The study aimed to report and discuss the normative data of the Italian version of ICS (ICS-I) in Italian-speaking preschool children, and to investigate whether the age influences the ICS-I scores (construct validity). Socio-economic status (SES) of the family were investigated and compared to parents' ratings on child's speech intelligibility.

Methods: A cross-sectional observational study was conducted. Italian-speaking children aged 3-6 years (n = 355; mean age = 56.06 months; SD = 9.8 months), without major developmental impairment, were recruited in kindergartens throughout a convenience sampling. Parents completed a self-report form on their family SES (educational level and employment status of fathers and mothers). Children were independently rated by their mothers (ICS-I_m) and fathers (ICS-I_f).

Results: Results show that ICS normative data for the Italian preschool population (ICS-I_m = 4.52; SD = 0.46; ICS-I_f = 4.47; SD = 0.49) are consistent with previous evidence found in other languages, suggesting that ICS could be a potential cross-linguistic tool to assess functional intelligibility. A statistically significant (p < 0.001) improvement in ICS-I score was found with increase of age (construct validity). No evidence of association (p > 0.05) with ICS-I was found for SES family.

Conclusion: The study provides normative data of the functional intelligibility assessed by a subjective parental scale. As for other previous international studies, ICS-I normative data suggest that a preschool child without major impairment shows a high degree of speech intelligibility, even if minimal differences of intelligibility are reported for different communicative partners. The current findings support clinicians and researchers in implementing ICS-I in typical and also in atypical population with different SES background and promoting its application as a potential outcome measure in children with Speech Sound Disorders.

Keywords: Functional intelligibility; Intelligibility in Context Scale; Norming data; Parent report; Speech assessment; Speech sound disorder.