Lead study author Cary Stothart said, "Although these notifications are generally short in duration, they can prompt task-irrelevant thoughts, or mind wandering, which has been shown to damage task performance. We found that notifications alone significantly disrupted performance on an attention-demanding task, even when participants did not directly interact with a mobile device during the task."
The researchers tested volunteers through an attention-monitoring test to reach their conclusions. Study participants were found to perform significantly worse on a task when their phones were buzzing or ringing. In fact, they were thrice more likely to make mistakes. The level of distraction was comparable to actually answering the phone call or writing a text message.
The researchers said, "If you really want to keep your mind on a task, just ignoring your phone notifications is not enough. You need to disable them altogether. While users initially believed the mobile devices would improve their ability to perform well with homework and tests and ultimately get better grades, the opposite was reported at the end of the study."