Rhotacism

For example: r’s may become burrs or guttural grunts or w’s or l’s (rhotacism); […]

From the analysis of Kana writings, hypothesizes that the inability to establish a stable… […] The correction of rhotacism by means of an electric vibrator.

It is universally accepted that the rhotacism, a defective utterance of the /r/ sounds, is usually the last and most difficult American English consonant to correct functionally. I use two methods to help correct the rhotacism.