When grown-ups are reading to toddlers, they have more meaningful conversations when the stories are in traditional printed books than when stories are in e-books, researchers found.
Results of the small experiment suggest story time with tablets may not be as good for kids' development.
Pediatricians recommend against any screen time at all for children under age two. They warn that tablets, smartphones and digitally enhanced toys and games can get in the way of creative play and interactions with caregivers that are essential for social, emotional and cognitive growth.
But many parents who don't sit kids down to watch cartoons or play video games may still use tablets to read e-books to young kids. Among other things, e-books can be more convenient than cramming lots of board books in a diaper bag. Many parents also believe reading apps and interactive e-books can make it easier for kids to learn their ABCs.
"We know shared book reading is such an amazing developmental activity to engage in with children - not only by exposing children to rich language and vocabulary, but also by providing opportunities for physical closeness and creating moments to bond," said lead study author Dr Tiffany Munzer of the University of Michigan's CS Mott Children's Hospital in Ann Arbor.
"Parents and toddlers know how to engage over a book, but when adding a tablet into the mix, it deflects from some of the positive benefits of that shared reading experience," Munzer said by email. "That isn't to say there is no benefit to electronic book, just less than when you compare it with a print book."
For the study, Munzer's team videotaped 37 parent-child pairs during reading sessions done in a lab. Parents read similar stories in three different formats: traditional printed books, e-books without any bells and whistles, and "enhanced" e-books with extra features like sound effects or animation.
During each reading session, researchers observed how much interaction, conversation and collaboration happened between parents and kids.
With printed books, parents talked to kids much more about the stories. The grown-ups paused to do things like ask kids if they remembered something they did that's similar to what's happening in the story, or asking kids what they think will happen next, the researchers report in Pediatrics.
Enhanced e-books sparked more interactions than e-books without any bells and whistles, however.
Toddlers also spoke up more to ask questions and share their own opinions and ideas about the stories when parents were reading from printed books.
The enhanced e-books sparked more interaction initiated by kids than basic e-books, however.
The study can't say whether or how specific book formats might directly impact kids' social, emotional or cognitive development. It also wasn't designed to determine whether different formats influence how easily or quickly children later learn to read.
One benefit of reading to kids is the "back and forth" dialog that can happen while parents are sharing a story with young children and help put the story in the context of the child's life experiences, said Dr Suzy Tomopoulos of the department of pediatrics at New York University School of Medicine, in an email.
"For example, if the book is about a trip to the zoo, the parent can talk about their last trip to the zoo and the animals they saw," said Tomopoulos, who co-authored an editorial published with the study.
"Shared book reading with print books has been well studied and has been found to help child development, language, and social skills," Tomopoulos added. "One of the main problems with screens is that they interfere with these high quality parent-child interactions that would otherwise take place."