She taught at Indiana University – Purdue University Fort Wayne (1981-1985), Georgetown University (1985-1987), and Texas A&M University (1987-1997), followed by her current position of professor of rhetoric and linguistics at Carnegie Mellon University since 1997.[4]
Johnstone has also published papers on gender and language, Arabic language discourse, as well as many other linguistic topics.[5] On top of that, she also wrote a book called the "Linguistic Individual,"[6] discussing self-expression in language.
Johnstone is recognized as an expert on Pittsburgh English,[7] locally known as "Pittsburghese." Her research is concerned with how the dialect is "constructed through local talk, and talk about talk," connecting "people's understandings of language and place" with language change.[1] Her 2013 book Speaking Pittsburghese: The Story of a Dialect, is a summation of her scholarly work on Pittsburgh English.[1][8][9] The book is a sociolinguistic analysis of the history of Pittsburgh English and how it has changed over time, with a focus on the process of enregisterment and how the dialect is linked to local identity.[10] It also explores the history and local use of some of Pittsburgh's most emblematic words, including "yinz," "nebby," and "dahntahn."[11] Johnstone also focuses on phonological features of "pittsburghese" such as the monophthongal /aw/.[12]
Johnstone has written about style-shifting among Texas women. In her article, "Uses of southern-sounding speech by contemporary Texas women", Johnstone delves into how Texas women use different ways of talking, which range from "automatic and nonstrategic" to "very planned and strategic".[13]
In another article, titled "Sociolinguistic Resources, Individual Identities, and Public Speech Styles of Texas Women", Johnstone studied how women in Texas form linguistic identities based on their own individual backgrounds, such as ethnicity, region of living, as well as the linguistic models they experienced in their lives.[14]
