Learning to talk is one of the big milestones of childhood. Children usually learn to speak and understand language organically: it develops naturally from their interactions with and observations of others. As adults and older children talk with and read to them, toddlers respond — lifting flaps on books, finding their blanket, opening their mouths to eat and eventually, using words.

Gestures, facial expressions, and child-oriented language all help keep babies' attention and nurture their understanding of language. Many studies have shown that putting a child in front of a television, even when educational videos designed to introduce words and concepts to young children are on the screen, does not produce the same level of learning that face-to-face interactions do.

Social interaction is key. Children who simply watched a video demonstrating and using new words were far less likely to pick up and be able to use them.

A new study published in Child Development explains why. It also underscores just how important the social aspect of communication is. The research should help parents who have to travel for work feel a little better about having to use their smartphones to get a little face time with their toddlers.

“Interactions — such as live instruction and the video chats — allow adults and toddlers to respond to each other in a back-and-forth fashion.” researcher Sarah Roseberry said in a statement. “These types of interactions seem to be central for learning words.”

In the study, Skype Me! Socially Contingent Interactions Help Toddlers Learn Language, children from 24 to 30 months were taught new words by an adult in one of three ways. Some were introduced to the words by having a conversation about them in person; others saw the words explained in a video; and a third group participated in a Skype conversations with an adult much like the in-person conversation.

Children who actually interacted with the adults — whether through an in-person conversation or via video chat — were far more likely to learn the new words. Social exchange was key. Those who watched a video using the new words were far less likely to pick up and be able to use the new words.

Attention also did not seem to be a factor. Children did pay attention to the videos, but they didn't tend to learn from them. Responsive interaction and eye contact with the person using the words — and language — seem to be the active ingredients.

The study, by researchers from the University of Washington, Temple University and the University of Delaware demonstrates that when parents respond to their children in timely and meaningful ways, it helps them learn — even when mom and dad are on screen in a video chat. But if kids are just "parked" in front of a screen without the possibility of live interaction, very little real learning is likely to take place, no matter how educational its offerings.