An MRI-based analysis of the English /r/ and /l/ articulations

Midsagittal tongue shapes for sustained English /r/ and /l/ sounds between native speakers of American English (AE) and Japanese were compared using the magnetic resonance imaging (MRI) technique. The /r/ sound as produced by AE speakers was characterized by a constriction at the anterior part of the hard palate and the existence of a sublingual cavity, and for the /l/ sound, apical contact to the front teeth and/or alveolar ridge, and the absence of the sublingual cavity. For Japanese speakers, strategies to form the tongue shape contrast between /r/ and /l/ productions were categorized into four types depending on the type of contact/constriction and presence/absence of the sublingual cavity. The first type showed a pattern of tongue shape similar to AE speakers. The second and third types were characterized by /r/- and /l/-oriented production, respectively, for both sounds. In the last type, the distinction between /r/ and /l/ was formed only by the absence or presence of apical contact, while a sublingual cavity was produced for both sounds. These types are discussed in the context of a perceptual evaluation and an acoustical analysis