In this Aug. 29 photo, Kathy and Steve Dennis display their 1980's-era Apple II+ computer bought for their then young sons in Bellevue, Wash. Three decades ago they never heard the phrase "screen time," nor did they worry much about limiting the time the kids spent with technology, considering the computer an investment in their future. Things have changed with their grandkids and their phones.

NEW YORK—When Stephen Dennis was raising his two sons in the 1980s, he never heard the phrase “screen time,” nor did he worry much about the hours his kids spent with technology. When he bought an Apple II Plus computer, he considered it an investment in their future and encouraged them to use it as much as possible.

Boy, have things changed with his grandkids and their phones and their Snapchat, Instagram and Twitter.

Today’s grandparents may have fond memories of the “good old days,” but history tells us that adults have worried about their kids’ fascination with new-fangled entertainment and technology since the days of dime novels, radio, the first comic books and rock n’ roll.

True, the concerns these days seem particularly acute — as, of course, they always have. Smartphones have a highly customized, 24/7 presence in our lives that feeds parental fears of antisocial behaviour and stranger danger.

“When it was a TV set in the living room, you may not always have been checking it, but it was pretty easy to know if something upset them, or if they had questions,” said Peggy Cassidy, a media researcher at Adelphi University in New York who wrote a history of American kids and media. Now, she said, parents really have to be on their toes to stay on top of what — and who — their kids are exposed to online.