Linguistics

they were taking part in an unusual experiment, which involved tracking their own voices over time. This was done by making 10-minute recordings every few weeks. They would sit in front of a microphone and repeat the same 29 words as they appeared on a computer screen. Food. Coffee. Hid. Airflow.

One of those changes was the "ou" sound in words such as "flow" and "sew" that shifted towards the front of the vocal tract.

I'm not actually sure what sound change they're describing there. Can anyone explain with examples or IPA?

edit: Cheers for the answers (turns out I misunderstood which part is the vocal tract)

This is not bad

Hi, I'm a casual linguistics nerd (no degrees), speaking Philippine English with heavy American influence.

My accent of English has pre-nasal /æ/ raising and I've caught myself raising it in other places like before /g/.

When I look at English language learning videos (out of curiosity) I have not found anyone mention /æ/ raising in them.

Why is this case?

I'm sharing this mostly as a historical curiosity; Schleicher was genial, but the book is a century and half old, science marches on, so it isn't exactly good source material. Still an enjoyable read if you like Historical Linguistics, as it was one of the first successful attempts to reconstruct a language based on indirect output from its child languages.

Link for the Science research article. The observation that societies without access to softer food kind of avoided labiodentals is old, from 1985, but the research is recent-ish (2019).