A psycholinguistic approach to designing word stimuli for evaluating speech sound production in Persian-speaking children: Focus on face and content validity

There is a pressing need for well-defined phonological assessment protocols and the development of valid, reliable, and clinician-friendly tools tailored to the unique linguistic contexts of each country. This study reports the initial phase of establishing normative data on phonological development in Persian-speaking children aged 24-84 months. The objective was to develop a robust set of single words varying in length and syllabic structure for use in speech sound assessment. Using a content analysis approach, 108 words were selected, ranging from one to six syllables (35 monosyllabic, 26 disyllabic, and 47 polysyllabic). Word selection was guided by psycholinguistic principles, including phoneme frequency, phonotactic diversity, syllabic complexity, and lexical familiarity. Criteria ensured cultural appropriateness, absence of repeated phonemes, diverse syllable structures, and inclusion of all consonants across positions. The stimuli are designed to probe underlying speech motor planning and phonological encoding processes in children. These words were organized into 18 semantically related image sets, each containing six words. Monosyllabic and disyllabic items included at least two Persian consonants in both initial and final syllable positions, and each consonant was represented by at least one polysyllabic word. Eight clinically-experienced adults evaluated name-image agreement, while 10 children aged 30-54 months demonstrated over 50% spontaneous naming and over 70% familiarity with the words. The final stimulus set includes a substantial number of polysyllabic words and appears suitable for analyzing phonetic and phonemic inventories, and phonological error patterns in Persian-speaking children.