Phonics vs. whole-word instruction in a tone language: Spelling errors on consonants, vowels, and tones over age

Phonics vs. whole-word instruction effects on spelling proficiency were investigated for Thai, an alphabetic script that represents tonemes orthographically. Errors made by a cross-sectional convenience sample of 128 children aged 6, 8, 10, and 12 years old and 25 adults were categorized by grapheme category (Consonants, Vowels, Tones) and type (Reversals, Additions, Substitutions, Deletions). Fewer spelling errors were made by phonics-taught children who showed consistently better performance as a function of age. An additional quadratic component for the whole-word group suggested a different developmental trend involving a plateau after 8 years of age. Consonant errors were most frequent (but decreased rapidly over age), followed by vowel then tone errors. Vowels and tones were more dispensable than consonants, regardless of age or instruction method, suggesting that consonants may be of particular importance in Thai spelling. This preliminary observational dataset on spelling in tone languages may have implications for educational policy in Thailand.