That is brought up near the end of the article.

While teachers may be intending for these tools to be strictly educational, students often have different ideas. According to a 2014 study, which surveyed and observed 3,000 university students, students engaged in off-task activities on their computers nearly two-thirds of the time.

Horvath blamed this tendency to get off-track as a key contributor to technology hindering learning. When one’s attention is interrupted, it takes time to refocus. Task-switching also is associated with weaker memory formation and greater rates of error. Grappling with a challenging singular subject matter is hard, Horvath said. For the best learning to happen, it’s supposed to be.

“Unfortunately, ease has never been a defining characteristic of learning,” he said. “Learning is effortful, difficult, and oftentimes uncomfortable. But it’s the friction that makes learning deep and transferable into the future.”

Sustained attention to a singular subject is anathema to how technology today has been deployed, argues Jean Twenge, San Diego State University psychology professor studying generational differences and the author of 10 Rules for Raising Kids in a High-Tech World. More time on screens isn’t just ineffective in facilitating learnings; it’s counterproductive.

“Many apps, including social media and gaming apps, are designed to be addictive,” Twenge told Fortune. “Their business model is based on users spending the most time possible on the apps, and checking back as frequently as possible.”