By Jericka Duncan

PHILADELPHIA (CBS) — Chris Brown and Rihanna, back together?

“I know I heard their birthday cake song last night,” said Kelsie Martinelli of Temple University. “My roommate was listening to it. I don’t think she should be doing that.”

People on the street and on the internet are abuzz with comments. Brown used Twitter on Monday to wish Rihanna, whose first name is Robyn, a happy birthday. The 24-year-old singer responded by saying “Thanks!”

Both used Twitter to promote their collaboration on two new songs.

“It’s a song,” said Amber Davis. “It’s not like they’re getting married, or having kids. They can do whatever they want. It’s not our job to speculate on what should or shouldn’t be done.”

In 2009, Brown attacked his then-girlfriend Rihanna at a pre-Grammy party. He pleaded guilty to a felony charge and is still on probation.

Dr. Stephen Treat, with Relationship Council, has worked with celebrity couples for more than 30 years. He says that what Brown and Rihanna are going through is nothing new.

“It’s a very common trend,” said Dr. Treat. “Often, the couples come back together. Often, the abuse repeats.”

Dr. Treat went on to say that it could work–if they do the work and go to therapy together.

While the two celebrities may never again be an official couple, it’s obvious that these days, Brown and Rihanna are a lot closer and more comfortable making music.