Watch with your child. That is the lesson.

If you take one thing from this blog, take this: sit with your child when the video is on. Pause. Ask a question. Wait for an answer. That is not extra. That is the teaching.

Gabrielle Strouse, Katherine O’Doherty, and Georgene Troseth at Vanderbilt University tested this with three-year-olds. Parents who paused a video, asked questions, and invited the child to tell part of the story helped kids understand more and pick up more words than kids who just watched. An on-screen character who asked questions helped too — a little less than a live parent, but still more than a quiet show.

Watch with your child, pause, and talk. Do not press play and walk away.

Why a person beats a screen for the youngest kids

Babies and toddlers usually learn less from a screen than from the same lesson given by a real person. Researchers call this the video deficit. Daniel Anderson and Tiffany Pempek at the University of Massachusetts Amherst named it. Rachel Barr at Georgetown University later talked about it as a transfer problem: it is hard for a young child to take what they saw on a flat screen and use it in the real room.

Gabrielle Strouse and Jennifer Samson looked at many studies of children from birth to age six. On average, kids learned less from video than from a live person. The gap was bigger for children under three, and smaller after that. So video is a weaker teacher than you are — especially for the youngest — and it gets more useful as kids grow into preschool.

Patricia Kuhl at the University of Washington showed this with babies. Nine-month-olds learned new speech sounds from a live tutor. They learned almost nothing from the same material on video or audio. Later work from her group found babies can learn from a screen when another child watches with them. The screen is not magic. The people around it are.

What to do while you watch

Sarah Roseberry Lytle, Kathy Hirsh-Pasek, and Roberta Golinkoff found that toddlers learned new words from a video chat that answered them, and from a live person, but not from a recording that did not wait. The wait matters. So does a character who looks at the camera, asks a question, and leaves a quiet beat.

• Sit together. You do not have to narrate every second.
• Pause after a question. Count to three in your head.
• Ask simple things: What sound was that? Who needs help? What happens next?
• Repeat the same short episode. Alisha Crawley and Daniel Anderson found preschoolers understood more after watching the same Blue’s Clues episode several days in a row.

That last point is a relief. Repeating a favorite is not a failure. For this age, repeating is how it sticks.

The honest limit

Our videos are a helper, not a stand-in for you, for books, or for preschool. They work best for preschoolers, and they work best when someone who loves the child is on the couch too. That is not a slogan. That is what the studies keep saying.