When you see a child crying, what do you do? You wrinkle your brow, turn down the corners of your mouth and make reassuring sounds. That way the child can see that you get what he or she’s feeling. Same deal when your husband comes home with a leg in a cast or your best friend announces a divorce.

“We read other people’s emotions in part by mimicking their facial expressions.” So says David R. Neal, PhD, psychology professor at the University of Southern California, reporting to Web MD on April 25th. He says that facial mimicry is like a sixth sense, and if you can’t move your face, you lose this ability. “If you have a poker face because your muscles are paralyzed, you can’t read the emotions of others as well.” In other words, your ability to respond to another human with appropriate facial expressions lets you know how they feel.

Neal’s study compared people who had Botox injections with people who had Restylane injections. The Botox-injected people were significantly less accurate at reading others’ emotions than those who were injected with Restylane.

In reviewing the study, a New York plastic surgeon thinks that Neal presents an exaggerated view of what Botox does. “You can have normal facial expressions with Botox unless you blast a face with so much that you can’t move your forehead.” But that same surgeon admits that most people who get Botox injections are overtreated, which could be a reason for this miscommunication.

Injecting Botox is a science, but it is also an art. Your results will vary greatly, depending on your injector, and if you are careless in choosing an injector you may not only be temporarily stuck with a frozen forehead but also with droopy eyelids or overly-elevated eyebrows.

According to the American Society for Aesthetic Plastic Surgery, in 2010, Botox and Dysport injections were the number one minimally-invasive cosmetic procedure performed in the United States.