A video of a 10-month-old baby girl's emotional reaction to her mom's singing makes us wonder how much a baby can understand. Mary Lynne Leroux's eyes welled up with tears while her mother, Amanda sang a heartfelt rendition of "My Heart Can't Tell You No" by Rob Stewart.

Mary did not fuss or wail just like how babies cry. She listened quietly instead and appeared to be overwhelmed with emotion when she squeezed her eyes and tears ran down her cheeks. She looked increasingly emotional until her mom stops and finally comforts her.

Some viewers were quite concerned about the baby, wondering whether she was distressed out of sadness or fear, while others were just cherishing her adorable and emotional reaction. Amanda says she's shy to sing in public but at home she surely has found an appreciative fan.

The video has already amassed more than a million views. Watch how Mary Lynne chokes us all up with emotion here:

Source: YouTube.com/Ronnie Arricivita

Now we wonder where do all her emotions come from? What was she feeling or thinking at the time? Was she sad or fearful? There is a big difference between baby and adult emotions simply because emotions are connected to physical and cognitive development and since babies haven't gained the experience adults have had, the emotions cannot be the same way.

"Generally speaking, emotions begin in infancy in ways that look familiar but aren't true emotional experiences," Pamela Cole of Pennsylvania State University said. "It is not precisely clear when fear develops, but you don't really see fear in young babies. Fear is not an instinct, it is something that babies learn as they develop memory."

At Mary Lynne's age, she is beginning to express and recognize emotions. She is also learning to read other people's emotions. Babies her age looks at her parents' reactions in new, surprising situations to figure out how they would respond. Does this mean she might be feeling her mom's sadness? Did Amanda sing this song to Mary while she was still in the womb? Does this reaction mean she will grow up to be extremely emotional? Shouldn't her mom be singing more lively children songs to her instead, given that she seems to already know how Mary reacts to such sad song? What do you think?