Young children readily learn words from their parents, grandparents, and child care providers in live conversations, but learning from video has proven more difficult. A new study questioned why and found that it's the responsiveness of the interactions that's key: When we respond to children in timely and meaningful ways, they learn -- even when that response comes from a screen.

The study, by researchers at the University of Washington, Temple University, and the University of Delaware, appears in the journal Child Development.

Three dozen 2-year-olds were randomly assigned to learn new verbs in one of three ways: training with a live person, training through video chat technology such as Skype that allows audio and video interaction via screen between users at different locations, and watching a prerecorded video of the same person instructing a different child who was off screen and thus out of synch with the child in the study.

In the study, children learned new words only when conversing with a person and in the live video chat, both of which involved responsive, back-and-forth social interactions. They didn't learn the new words through the prerecorded video instruction, which was not responsive to the child.

Children who learned in the two environments that involved real-time social interaction even used the new words to label the actions when different people performed them.

"The study highlights the importance of responsive interactions for language learning," suggests Kathy Hirsh-Pasek, professor of psychology at Temple University, who coauthored the study. "Interactions allow adults and toddlers to respond to each other in a back-and-forth fashion -- such as live instruction and the video chats. These types of interactions seem to be central for learning words."

"The research has important implications for language learning," Hirsh-Pasek continues. "Children are less likely to learn from videos than from live, back-and-forth responsive interactions with caring adults. Young children are not good at learning language if they're merely parked in front of screen media."