People in Philadelphia speak with a distinctive Philly accent, and those who converse in sign language are no different. The area is known for having one of the most distinctive regional sign language accents, and two researchers based at the University of Pennsylvania are trying to figure out why.

In sign language, an accent is apparent in how words are signed differently—it’s a lexical difference, similar to how some Americans say “pop” while others say “soda,” explains Meredith Tamminga, one of the professors conducting the research, in a statement.

Jami Fisher, her co-researcher, told PRI that many words in Philadelphia sign language are different from the American Sign Language standard. She added:

“The sign for hospital is exceptionally different from what standard ASL would be, among other things. To the point where the signs are not able to be deciphered based on what they look like… People say, ‘Oh, you talk weird,’ or, ‘You sign strange.’”

In many ways, Philadelphia sign language is more French than ASL. As PRI reports, the first sign language teacher in the United States, Laurent Clerc, was a Frenchman. ASL has evolved to a distinctive American sign language over time, but the Philadelphia version maintains more of its French roots.

Fisher and Tamminga want to figure out exactly why Philadelphia has such a strong accent, and so they’re planning to interview 12 members of the Philadelphia deaf community, from several different generations. They’ll annotate the interviews, a process that typically includes detailing sign start and end time codes, start and end hand shape labels for each hands, and articulatory sign classifications, which takes around two hours for every minute of sign language recorded.

Their theory as to why Philadelphia has such a distinctive sign language could also explain why this accent is fading. Philadelphia opened a school for the deaf, headed by Clerc, in 1820, and many deaf students in Philadelphia were educated at the school until it closed in 1984.

For this period, Fisher believes much of the language stayed largely the same. She said:

“Philadelphia deaf community members tend to say put, and when that happens you don’t have contact with other signing deaf, who are using what we now call American Sign Language, ASL. And when that happens, your language doesn’t change that much.”

By the mid 1980s, partly thanks to the increase of cochlear implants and education-policy changes, more deaf students were assimilated into mainstream public schools rather than attending boarding schools for the deaf. Fewer deaf teachers were also hired, and so students were more likely to see signing from an interpreter who was not native to Philadelphia’s style of signing.

As well as studying the sign language, Fisher hopes to preserve it. “In the community, long before me, people have been saying we need to document this, we need to get these people on video,” she said. “Some people are older and are passing away. We need to get this to preserve our language.”