TL;DR: Even if you don't look at your phone, the ding or buzz of a single notification is enough to derail your focus. We found that just receiving a notification degrades performance on an attention-demanding task as much as actively using the phone to text or talk.
The Hidden Cost of "Just Waiting"
We all know that texting and driving is dangerous. We’ve been told that using a phone during a critical task divides our attention and leads to mistakes. The common advice? "Just wait to respond. Put the phone down and focus."
But what if that advice is wrong?
The study complicates the standard advice. The distraction starts before you pick the phone up, the moment you hear the notification.
The findings speak to how we manage "connectedness." In any environment that demands sustained focus, our policies and personal habits ignore the cognitive cost of the notification itself.
The "Mental Echo" of an Interruption
We hypothesized that the brief sound or vibration of a notification acts as a trigger. The interruption outlasts the sound itself: it prompts "task-irrelevant thoughts," or mind wandering.
Your brain can't help it: who was that, is it urgent? And then you park a reminder to check later.
This last thought (the simple act of "remembering to check later") is a known cognitive burden called a prospective memory demand. It effectively opens a new, distracting "tab" in your brain, stealing attentional resources from the task at hand. Your body might still be "on task," but your mind has wandered.
How a Simple Game Revealed a Major Flaw
To test this, we had participants perform a simple task designed to measure sustained attention. This "Sustained Attention to Response Task" (SART) required them to watch numbers flash on a screen and press a key for every number except the number 3.
This task is easy to do, but hard to do well for long. It requires constant, low-level focus, and any lapse in attention results in a "commission error," which is pressing the key when you shouldn't.
Participants were split into three groups:
- Call Group: Received phone calls during the task.
- Text Group: Received text messages during the task.
- Control Group: Received no notifications.
Critically, all participants used their own phones. We got their numbers from a standard electronic check-in sheet they completed when they arrived, which also collected other demographic information. They had no idea this was related to the experiment or that the study was about cell phones. This meant they assumed the calls and texts were real, personal, and relevant.
The notifications were sent automatically by the experiment program itself, which used the Twilio application programming interface to send the calls and texts at precise moments during the task. This automation also handled condition assignment, so the experimenter in the room was blind to which group the participant was in.
And most importantly, we excluded data from any participant who actually looked at or handled their phone, isolating the precise, cognitive cost of the notification alone.
The Shocking Results: A Distraction as Bad as Texting
The findings were definitive. The groups that received notifications (both calls and texts) saw their performance collapse.
- More Mistakes: The notification groups made significantly more commission errors (pressing the key for "3") in the second block than the control group. Their sustained attention had failed.
- More "Automatic" Responding: The call group also showed a huge spike in "anticipations" (responding so fast that they were clearly just pressing the key out of rhythm, not in response to the number). This suggests their minds were elsewhere, and their fingers were just running on autopilot.
The observed distraction was comparable in size to the performance costs seen in studies of texting and driving.
Why This Matters for Anyone Who Needs to Focus
These findings have practical implications for daily life, work, and learning.
For Focused Work and Learning
Anyone trying to perform "deep work" (like writing a report, coding, or studying for an exam) is engaging in a sustained attention task. Our research suggests that a "silent" phone buzzing on the desk can be enough to disrupt concentration and affect performance. Even if you don't look, your mind may not be fully on the task, making learning less efficient and the quality of your work lower.
For Important Conversations and Decisions
Think about any situation that demands your full presence, like an important meeting, a difficult conversation, or trying to make a complex decision. This research suggests that an ignored notification can pull your focus away from the present moment. A fraction of your cognition may now be consumed by "Who was that?" and "What do they need?" In moments where nuance and full attention are beneficial, your focus may be compromised.
For Everyday Attentional Tasks
This applies to any task that requires monitoring, like driving, cooking a complicated meal, or watching children. These are, at their core, "Sustained Attention to Response Tasks." This study suggests that a single, "harmless" notification from a personal device can be distracting and may create an opening for errors, whether it's a missed stop sign, a burned dinner, or a missed danger.
The bigger cost is the interruption, not the interaction. Putting the phone down isn't enough if it can still go off.
Full Citation
Stothart, C., Mitchum, A., & Yehnert, C. (2015). The attentional cost of receiving a cell phone notification. Journal of Experimental Psychology: Human Perception and Performance, 41(4), 893–897. https://doi.org/10.1037/xhp0000100