By now we know that we’re (mostly) not supposed to multitask — that we can’t do two things at once very well and that it takes us a while to refocus when we switch from one task to another. This is why we put our phones screen-side down and slightly out of reach when we want to focus on something or show someone that we’re paying attention. But unless your phone is fully silenced or off, it’s probably still distracting you. The familiar buzz buzz of a new notification is not as innocuous as it seems.

This may sound intuitive. But many people (including myself) might not realize just how beneficial switching from vibrate to silent can be. A new piece of research, “The Attentional Cost of Receiving a Cell Phone Notification,” reports that the reverberations of new notifications can distract us, even when we don’t look over to see what they could be. It found that just being aware of an alert can hurt people’s performance on an attention-demanding task.

The authors, Cary Stothart, Ainsley Mitchum, and Courtney Yehnert of Florida State University, became interested in the impact of these notifications after noticing that they themselves got distracted by them.

“If we were driving and we felt a vibration for a phone call, that led us to think about the source of that call — who it could be, what the message was,” Stothart told me.

They knew from the literature on distracted driving that talking on the phone causes a cognitive load, which means it requires a certain amount of mental effort and working memory. Multitasking, for example, imposes a heavy cognitive load and hurts performance on a task, because our mental resources are finite and have to be allotted to discrete tasks. That’s why you’re not supposed to talk on the phone or text while you’re driving, and why many campaigns urge drivers to wait to respond until they’re no longer behind the wheel.

This led the authors to think that an alert or notification could also cause cognitive load, because that buzzing might make you wonder about the content or source of the message. So even if you wait to respond until you finish what you’re working on, the fact that you’re aware of something waiting for you could be enough of a distraction to make you perform worse than you would had you not received a notification.

In 2013, they recruited 212 undergraduate students at FSU to participate in an experiment. The students would come to their lab, provide their phone numbers, emails, and other information, and then complete a Sustained Attention to Response Task (SART). This measures sustained attention, or your ability to focus on one task without drifting off and thinking about something else. The task had students press a key any time a number flashed on a computer screen, unless that number was “3.” They did this for about 10 minutes — this was the first “block” of the task that gave researchers a measure of baseline performance —and then they had a minute-long break. Meanwhile, a computer had randomly assigned participants to one of three groups. So after the break, one-third of participants started receiving text messages as they completed the SART a second time (the second block), while one-third received phone calls, and another third served as a control and didn’t get anything.

Participants completed the experiment individually, with one experimenter in the room to note if anyone actually took out his or her phone. Since the researchers were only interested in how the knowledge of receiving a notification affected performance, they excluded people who interacted with their phones from the analysis. The experimenter didn’t know beforehand which people would get notifications, as a computer sent those out randomly.

The students weren’t told to leave their phones out or unsilenced or anything, but they were asked afterward if they had heard or felt the notifications. Stothart said that because people were divided into groups randomly, they could assume an approximately equal number of people had their cell phones, didn’t have their cell phones, or had them on silent — so the researchers were confident in looking at the main differences in performance among groups.

They measured performance by looking at the number of commission errors (someone pressed a key for “3” when they weren’t supposed to) during both blocks of the task and across the groups. These errors are analogous to action slips — so for example, say you’re writing an email to your colleague explaining next steps for a project, and you accidentally type “pizza” instead of “plans” because you suddenly thought about lunch. That’s an action slip. According to Stothart, when they compared the first block of the task to the second block, the probability of making an error increased by 28% in the group that received phone calls. For the group who got text messages, they made 23% more errors than they did during the first half of the experiment. And the group who received no notifications made 7% more errors. “That comes, we think, just from task fatigue,” Stothart said. “So if you’re doing this tedious task for a while, your performance declines regardless of whether or not you receive notifications.”

Were these results statistically significant? Short answer: Yes. Long answer: When the researchers looked at the relationship between block and group, they found that the percent change between blocks was greater for participants who received notifications, compared to participants who didn’t, and this was statistically significant at the 0.05 level. However, they didn’t find any significant difference in errors between people who received phone calls and people who received texts.

So basically, just having your phone near you can distract you and negatively affect your work performance. And this distraction-by-notification might even be comparable to interacting with your phone. Stothart said that in terms of effect size, their results were consistent with those of the distracted driving literature, which has looked at the effects of texting or talking on the phone (interacting) while driving. But what they weren’t able to pinpoint was what was actually behind the distraction.

“We think that the mechanism behind the distraction from knowing that you received a notification is mind wandering, but we haven’t actually looked at that in our study,” Stothart said. “It could just be prospective memory, or knowing that you need to do something in the future, that impacts performance. So the next step for us is to disentangle that — to actually determine if the mechanism behind our effect is mind wandering or something else.”

Regardless, if you want to stave off distraction and be able to perform a task at your very best, the researchers say it couldn’t hurt to put your phone on silent, or hide it so that you can’t hear, feel, or see any notifications. Maybe this isn’t that surprising. But digital distraction has been dubbed, “the defining problem of today’s workplace,” and our phones lie at the heart of that. For how relatively nascent smartphone ubiquity is, the line of research devoted to understanding its effects is far-reaching. You can read about how phones destroy our productivity, how their mere presence distracts us, and how phantom vibrations are a thing. And as we start getting more and more notifications (they’re the next big platform after all), we should be conscious of how the habitual buzz buzzing of our devices affects our ability to concentrate at work.