The research, carried out by the Kaiser Family Foundation in the US, also discovered that youngsters aged between eight and 18 are always using some electronic device when they are not in school.
Some use more than one device at a time and consume over 10 hours of electronic content a day.
The "electronic life" of children has "exploded" in the last five years because portable devices have completely changed the way children access television programmes, films and music.
The findings of the study have upset child welfare experts.
"It's a very sad state of affairs and I hope the research will be a wake-up call for some parents. As far as some people are concerned these devices have become like an opiate designed to keep children quiet," Times Online quoted Michele Elliott, a child psychologist and founder of the child welfare charity Kidscape, as saying.
Elliott added: "When children are using these devices they are not communicating or interacting with anyone else [in person]. They may be very good at texting but how do they do when they have to meet someone face to face?
"Parents need to limit the amount of time young children use electronic media."
Experts have different opinions on the effect of such heavy usage of gadgets on children's health, emotional wellbeing and social skills.
However, not everyone is cynical.
"We need to focus not just on the fact that children are using screens but what they are using them for. What they are doing is often quite creative and quite interactive," Professor Rupert Wegerif, director of research at the school of education and lifelong learning at the University of Exeter said.