Here's how they make babies cry in TV and movies

• Babies and young kids are cast in movies just like adult actors, but there are special rules in place about how long they can be on set.
• Oftentimes, a director wants a baby to cry on camera, and real babies are used for many of the scenes.
• We spoke with a professional baby wrangler named Elaine Hall, who has a trick she says works every time to make an infant cry on cue.

Following is a transcript of the video.

Narrator: Babies cry all the time, whether you like it or not. And it takes a very patient parent to make them stop. When it comes to TV and movies, however, a director may actually want a baby to cry on command. And this requires hiring someone with a special set of skills.

That's Elaine Hall. She's what's known in Hollywood as a baby wrangler.

Elaine Hall: A baby wrangler is a interpreter between what the director wants a young child to do in front of a camera.

Narrator: She's worked with infants and young children on a variety of commercials, TV shows, and movies, like "The Flintstones," "Grace Under Fire," and "Akeelah and the Bee."

First off, where do these crying babies come from?

Babies, just like adult actors, come from casting calls, but they're only legally allowed to work for four hours a day on set, so there's a simple trick used to extend their camera time.

Hall: Very often, when you see a TV show or a film, twins are used to play one role.

Narrator: There's also a few other rules in place when using young actors.

Hall: For every set that has a child, there's a studio teacher on the set. For infants, there must be a studio teacher and a nurse.

Narrator: For non-crying scenes, working with babies and young children involves making it fun for them. Hall: Everything was made into a game. I would put on the lens of the camera, funny faces on the lens, when they needed to make direct eye contact. I would be behind the camera on every scene, making them laugh.

Narrator: But for crying, it's a whole different story. Elaine uses a special technique.

Hall: What I do to get babies to cry is, I start to cry myself. For example, I'll go, "Wahhhh!" And the baby will start to cry. When a baby, even an infant, hears another baby cry, the infant or the baby will start to cry themselves. This is an example of empathy. It's pretty instantaneous.

Narrator: She used this technique in "Akeelah and the Bee." In this scene, Akeelah's sister brings her baby to the event, and it starts to cry. And her technique has never failed, so far.

Hall: My success rate is 100 percent.

Narrator: She says she's heard of other baby wranglers using questionable techniques like placing bad odors in front of the child or making a loud noise. But according to Elaine, these sorts of methods may be harmful to the child, and should be avoided.

If the baby's face doesn't need to be shown on camera, oftentimes, they'll use a doll instead.

Once it's crying, how do you get the baby to stop?

Hall: When I stop crying, and then I'll look at the baby, and assure the baby that everything's safe, I'm okay, she's okay, then, very quickly, a baby will stop crying.

Narrator: She may also use rattles and bells to help, if necessary.

Regardless of the scene, Elaine says it's important that the baby spend time with the actor ahead of time.

Hall: I always have the actor and the baby create relationship off camera, so that it's not like you're just plopping a kid into a stranger's lap.