“He makes me set the timer on the microwave,” Ms. Wade said. “And when it dings he’ll say, ‘Come on,’ and he’ll say, ‘Don’t bring your phone.’ ”

Image Jeanne Pyrz texts as her son, Dwyer, 3, plays. Credit... William Zbaren for The New York Times

Not all child-development experts think smartphone and laptop use by parents is necessarily a bad thing, of course. Parents have always had to divide their attention, and researchers point out that there’s a difference between quantity and quality when it comes to conversations between parents and children.

“It sort of comes back to quality time, and distracted time is not high-quality time, whether parents are checking the newspaper or their BlackBerry,” said Frederick J. Zimmerman, a professor at the University of California, Los Angeles, School of Public Health who has studied how television can distract parents. He also noted that smartphones and laptops may enable some parents to spend more time at home, which may, in turn, result in more, rather than less, quality time overall.

There is little research on how parents’ constant use of such technology affects children, but experts say there is no question that engaged parenting  talking and explaining things to children, and responding to their questions  remains the bedrock of early childhood learning.

Betty Hart and Todd R. Risley’s landmark 1995 book, “Meaningful Differences in the Everyday Experience of Young American Children,” shows that parents who supply a language-rich environment for their children help them develop a wide vocabulary, and that helps them learn to read.

The book connects language use at home with socioeconomic status. According to its findings, children in higher socioeconomic homes hear an average of 2,153 words an hour, whereas those in working-class households hear only about 1,251; children in the study whose parents were on welfare heard an average of 616 words an hour.

The question is: Will devices like smartphones change that? Smartphone users tend to have higher incomes; research from the Nielsen Company shows that they are twice as likely to make more than $100,000 a year than the average mobile subscriber. If increased use of technology encroaches on the time that well-to-do families spend communicating with their children, some could become the victims of successes originally thought to help them.