Speech with a drawl, twang, clipped consonants, broad vowels, slurred words or extra diphthongs might give away that the speaker is from the American South, Boston, the Midwest or elsewhere. The spice that a certain region may lend to spoken language can even be strong enough to flavor non-audible language as well. Indeed, American Sign Language (ASL) has its own accents. And like its audible counterpart, one of the strongest regional accents in ASL is that of Philadelphia residents, reports Nina Porzucki for PRI.

Related Content Here’s Why French People Are Getting Riled Up About the Circumflex

Researchers based at the University of Pennsylvania are documenting Philly ASL and asking exactly what makes it special. Leading the effort is linguistics lecturer Jami Fisher, who has a unique connection to the language: Her parents and her brother are all deaf, so she grew up signing in Philadelphia. She says she doesn’t sign with her hometown's accent, but she does understand it.

"When most people talk about a dialect, in spoken languages and sign languages too, a lot of what they center on are lexical differences, differences in words," Fisher tells PRI. "For example, the sign for hospital is exceptionally different from what standard ASL would be, among other things." She says that someone from another part of the country wouldn’t recognize some of the signs used by Philly ASL signers.

This striking difference comes from how sign language came to the United States, the researchers suspect. Before 1814, there was no standard American Sign Language. That started to change when a Connecticut minister, Thomas Hopkins Gallaudet, helped found a school now known as the American School for the Deaf. The co-founder of the school, Laurent Clerc, came from a school in Paris, so ASL is heavily influenced by French Sign Language.

Another school for the deaf opened in Philadelphia in 1820, with Clerc serving as one of its first principals. The school was popular enough that it expanded to a 33-acre campus at Mt. Airy, where it remained for 92 years, providing schooling as well as room and board for its students. It was that immersive, isolated environment that gave rise to the Philly ASL dialect, the researchers suspect. The dialect is strongest in the older members of the Philadelphia deaf community, many of whom attended the school. "We think that these older signers are signing in a way that is pretty similar to how it was longer ago, in the late 1800s and early 1900s," Fisher says.

But the Philly ASL accent - like the Philly oral accent - is in danger of disappearing. The researchers are working to videotape their interviews with Philadelphia’s deaf community (aided by Fisher’s father, who knows many of the people they are interviewing) and annotating the videos to preserve the uniqueness of Philly ASL, reports a press release from the University of Pennsylvania. Fisher notes that similar projects are happening in Australia, Brazil, Ireland, France, the Netherlands and beyond.