In what way is Pygmalion is a play about speech and phonetics?
Two of the main characters in the play, Henry Higgins and Colonel Pickering, are experts in linguistics. The main plot elements of the play revolve around Higgins' bet with Pickering that he can use his expertise as a teacher of applied linguistics to take Eliza Doolittle, a flower seller living in dire poverty, and pass her off as a Duchess. As Shaw mentions in his Preface, the character of Higgins is modeled to a certain degree on Henry Sweet, a distinguished and eccentric English philologist and phonetician.
The underlying issue behind this is that accent is a clear class marker within Britain, and that people's accents give away not just their geographical background but also their socioeconomic one. For Shaw, speech is not only a socioeconomic marker, but also a way of shaping thought. As Eliza becomes increasingly adept at new ways of speaking and learns the manners of the upper middle classes, she develops habits of deliberation and restraint, as well as a new language, and becomes unable to regress to her old self. As she states:
I can't. I could have done it once; but now I can't go back to it. Last night, when I was wandering about, a girl spoke to me; and I tried to get back into the old way with her; but it was no use. . . . I have forgotten my own language, and can speak nothing but yours.