The Japanese Version of the Functional Listening Index—Paediatric (FLI-P(J)): Translation, Normative Data, and Clinical Feasibility

Background: The Functional Listening Index—Paediatric (FLI-P) tracks functional listening development from birth to six years but lacks Japanese-language norms. This study translated the FLI-P into Japanese (FLI-P(J)) to generate normative developmental trajectories for typically hearing children. Methods: Following translation, the FLI-P(J) was administered as an online caregiver survey in Japan. After applying sequential exclusion criteria (removing developmental concerns, zero scores, and IQR outliers) to 2976 responses, a normative sample of 2512 typically hearing children (2–73 months) was retained. Four parameter logistic functions were fitted to empirical percentile trajectories (5th–95th). Results: FLI-P(J) scores demonstrated rapid growth across the first three years before gradually plateauing. Phase-level acquisition curves confirmed the expected developmental ordering. Most clinically flagged children scored at or below the 5th percentile. Conclusions: This study establishes the first Japanese normative reference curves for functional listening. This cross-linguistic alignment, together with preliminary evidence that clinically flagged children scored at the low end of the distribution, supports the potential of the FLI-P(J) as a clinical benchmark for evaluating Japanese children who are deaf or hard of hearing, pending further validation in independently confirmed clinical samples.