[ATR] feature involves a distinct tongue root articulation: Evidence from ultrasound imaging

• [+ATR] vowels have a more anterior actual tongue-root position than [−ATR] vowels.
• Results hold for high, mid, low vowels in Dagbani.
• Dominant [+ATR] value has tongue-root advancement from a neutral position.
• Tongue-body height does not account for distinction between [+ATR] and [−ATR] vowels.
• Results support Direct Mapping Hypothesis.

The feature [ATR] (Advanced Tongue Root) assumes a unique role of the tongue root in the production of [±ATR] vowels. However, whether the actual position of the tongue root accurately characterises vowel pairs distinguished by this feature has attracted some controversy. This paper tests the hypothesis that the [ATR] specification of a vowel maps onto a definite articulatory position of the tongue root. It further investigates whether such a mapping reflects which of the values of [ATR] is dominant in a language. The results of five ultrasound imaging experiments using Dagbani, a Gur language of Ghana, show that [+ATR] vowels of all height specifications are produced with a more anterior tongue root than [−ATR] vowels. They also show that tongue body height, a plausible alternative to tongue root position, does not consistently define the distinction. More importantly, the results show that vowels specified for [+ATR], the dominant value in Dagbani, are produced with a tongue root anterior displacement from a neutral position while the recessive [−ATR] vowels have variable tongue root positions. The results support a direct mapping between the phonological feature [ATR] and the articulatory gestures producing it.