The distraction caused by a notification - whether it is a sound or a vibration - is comparable to the effects seen when users actively use their cell phones to make calls or send text messages, they said.
"The level of how much it affected the task at hand was really shocking," said Courtney Yehnert, a Florida State University (FSU) research coordinator.
"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," the researchers said.
"Cellular phone notifications alone significantly disrupt performance on an attention-demanding task, even when participants do not directly interact with a mobile device during the task," they said.
The study underscores that simply being aware of a missed call or text can have the same effect.
The findings are significant because many public information campaigns intend to deter problematic cellphone use - while driving, for example - often emphasise waiting to respond to messages and calls.