Perceptual asymmetries in the development of lexical tone perception in Thai-learning children

Discrimination of vowel and consonant pairs is influenced by their order, known as perceptual asymmetry, and recent research suggests a similar effect for lexical tones. This study tested whether discrimination of two consecutive tones is easier when a dynamic contour tone (e.g., rising/falling) precedes a static-level tone (e.g., low/high) than vice versa. Thai-speaking children aged 4, 6, and 8 years and adults completed an AX task with four tone pairs in dynamic-static and static-dynamic orders. Adults showed no perceptual asymmetry, possibly due to ceiling effects. However, children in all three age groups discriminated dynamic-static pairs better than static-dynamic pairs. Although tone discrimination improved across age groups, the magnitude of the dynamic-static over static-dynamic advantage remained stable. These findings reveal a dynamic-static bias in tone perception that emerges before age four and remains stable into the school years. Implications for segmental asymmetries and theories of speech perception are discussed.