One highly debated question in Japanese phonetics is whether the rhotic ‘/r/’ should be classified as a flap or a tap (Vance, 1987; Okada, 1999; Arai et al., 2007) – the consonants distinguished by tangential vs. direct movement trajectories of the active articulator with respect to the passive articulator (Ladefoged & Maddieson, 1996; Derrick & Gick, 2011). Although the flap is considered to be the primary allophone in some descriptive accounts (e.g., Okada, 1999), articulatory evidence for flapping has been limited (Sudo et al., 1972 based on electropalatography, EPG) or appeared to be absent altogether (Maekawa, 2023 based on dynamic MRI). The methods used in these and other studies, however, did not always allow for an examination of the tongue tip movement or its contact with the palate with sufficient temporal and/or spatial resolution. These studies have also frequently largely considered /r/ flanked by vowels and thus being strongly coarticulated (cf. Katz et al., 2018).

In this talk, I revisit the question of flapping vs. tapping by examining fine-grained dynamics of the Japanese rhotic productions in two corpora of read speech – the X-ray microbeam (XRMB) speech production database of Japanese (Hashi, 2000, 19 speakers, 144 tokens) and the EPG Cross-Language Articulatory Database (Kochetov et al., 2017, 5 Japanese speakers, over 1800 tokens). The results show that flap realizations of the Japanese rhotic are considerably more common than previously reported. This was specifically the case in utterance-initial position, where all speakers in the XRMB corpus produced at least some rhotic tokens with a preparatory raising/retraction of the tongue tip, followed by a rapid downward/fronting movement of the articulator in the proximity of the alveolar ridge. Similarly, three out of five speakers in the EPG corpus produced many word-initial rhotics with a closure advancing from the postalveolar to front alveolar regions. In both sets of data, the following back vowels favoured flapping, while the following front vowels, as well as the intervocalic position, favourred tapping.

Based on these results, we may conclude that the Japanese rhotic is inherently a flap (cf. Okada, 1999), as this configuration is presumably its intended articulatory target. The tap allophone appears in contexts less favourable for flapping due to the stronger overlap with neighbouring vowel gestures. This is reminiscent of the variation found for North American English flap/tap allophones of /t, d/ next to rhotics and non-rhotic vowels (Derrick & Gick, 2011) and is broadly similar to the cross-linguistically common appearance of tap/approximant realizations of phonemic trills in aerodynamically unfavourable contexts (Ladefoged & Maddieson, 1996).