Baby babbles in sign language with deaf grandparents

Jane McCullough, a 6-month-old baby, has watched her parents and grandparents, who are both deaf, communicate using American Sign Language her entire life.

So when her grandparents speak to her, Jane babbles back to them in sign language too.

A video of Jane "signing" with her grandparents, Michael and Jessica Stultz, has gone viral on TikTok , with over 9 million views.

Jane's mom, Mara McCullough, told " Good Morning America " that she saw her daughter first start babbling back in sign language at around 4 months old.

She said it was something she and her brother did as well when they were infants.

"It's actually a really common thing," McCullough told "GMA." "For babies that are in a deaf household or a household where American Sign Language is used daily, babbling in sign language is really normal."

McCullough said she and her husband and Jane live with her parents in St. Augustine, Florida, so Jane is exposed to sign language every day.

"She’s been pretty alert and observant since the day she was born so we knew it was coming," McCullough said of Jane picking up sign language, adding that her parents were "really excited" to see Jane reacting to their conversations with her.

McCullough said she was surprised to see the video go viral with over 9 million views, but said she's glad more people are learning about American Sign Language, a "language expressed by movements of the hands and face," according to the National Institutes of Health.

"I think it’s been really eye-opening for people to see that babies are able to grasp language and that they’re so intelligent," McCullough said. "I think a lot of people already knew that babies can use sign language before they speak, but I think to see her babbling in sign language took things to a new level for a lot of people."

She added of Jane, "Just like how a hearing baby babbles in spoken language, she's doing it with her hands."