rhinoglottophilia
this is just a reminder to myself to investigate more about this when I have time. How would a direct realist (or even a motor theorist) respond to a sound change where V becomes nasalized after a voiceless fricative (in the absence of any nasal consonant) due to rhinoglottophilia? Does L&M talk about any such changes?
Come to think of it, the development of tones from voiced/voiceless stops presents a very similar problem to these perception theories.