The average office worker gets 120 emails a day and spends 2.6 hours reading and answering them. And that’s not factoring in the steady stream of instant messages, reminders, and alerts.

What is the impact of these interruptions on users’ task performance and emotions? Distinguished McKnight University Professor Joseph Konstan, whose work addresses human-computer interactions, decided to find out.

His team asked 50 study participants to do counting and reading comprehension tasks, then interrupted them at key intervals with news headlines and stock market updates flashing across their screens. The outcomes were revealing: Participants performed tasks more slowly when interrupted, and their levels of annoyance and anxiety varied by when they were interrupted.

“If you need to add up 25 lists of numbers and get interrupted at the end of a list, it’s easy to pick up where you left off,” says Konstan, the associate dean for research at the College of Science and Engineering. “But getting interrupted halfway through a list means you need to reload cognitively.”

The findings underscore the need for computer systems that predict opportune moments for gaining users’ attention. “While not all interruptions are bad, adjustments in technology could help people work more effectively,” he says.