(CNN) -- FaceTime, the Apple video-chat application, is not a replacement for real human interaction, especially for children, according to a new study.
Tween girls who spend much of their waking hours switching frantically between YouTube, Facebook, television and text messaging are more likely to develop social problems, says a Stanford University study published in a scientific journal on Wednesday.
Young girls who spend the most time multitasking between various digital devices, communicating online or watching video are the least likely to develop normal social tendencies, according to the survey of 3,461 American girls aged 8 to 12 who volunteered responses.
The study only included girls who responded to a survey in Discovery Girls magazine, but results should apply to boys, too, Clifford Nass, a Stanford professor of communications who worked on the study, said in a phone interview. Boys' emotional development is more difficult to analyze because male social development varies widely and over a longer time period, he said.
"No one had ever looked at this, which really shocked us," Nass said. "Kids have to learn about emotion, and the way they do that, really, is by paying attention to other people. They have to really look them in the eye."
The antidote for this hyper-digital phenomenon is for children to spend plenty of time interacting face-to-face with people, the study found. Tweens in the study who regularly talked in person with friends and family were less likely to display social problems, according to the findings in the publication Developmental Psychology.
"If you eschew face-to-face communication, you don't learn critical things that you have to learn," Nass said. "You have to learn social skills. You have to learn about emotion."
The Stanford researchers were not able to determine a magic number of hours that children should spend conversing per week, Nass said. Social skills are typically only learned when children are engaged and making eye contact, rather than fiddling with an iPod during a conversation, he said.
FaceTime and Skype are not replacements for actual face time because other studies have found that people tend to multitask while on video calls, Nass said.
Nass is a self-described technologist of 25 years, who has worked as a consultant with many major electronics firms, including Google and Microsoft. He said the findings disturbed him.
A few years ago, Nass worked on a study about how multitasking affects adults. He found that heavy multitaskers experience cognitive issues, such as difficulty focusing and remembering things. They were actually worse at juggling various activities, a skill crucial to many people's work lives, than those who spent less time multitasking, Nass said.