In 2017, a study from the Journal of the Association for Consumer Research confirmed that the simple act of having a smartphone in our presence decreases our cognitive performance. Here’s a breakdown of the effects of smartphone presence on our minds, and what we can do to reduce the negative effects.
According to the study, titled Brain Drain: The Mere Presence of One’s Own Smartphone Reduces Available Cognitive Capacity:
Results from two experiments indicate that even when people are successful at maintaining sustained attention—as when avoiding the temptation to check their phones—the mere presence of these devices reduces available cognitive capacity. Moreover, these cognitive costs are highest for those highest in smartphone dependence.
Previous studies in consumer research found that our cognitive abilities are largely determined by a limited amount of attentional resources. The abilities in question include working memory, reasoning, and problem-solving. The report’s initial hypothesis was that the presence of our smartphones may use up some of these limited resources, “thereby leaving fewer resources available for other tasks.”
Note that we’re not talking about using the phone, hearing it ring, or feeling it vibrate (prior studies found that all of these negatively impact our cognitive performance). It simply has to be in your presence.
The two studies had 548 and 296 undergraduate student participants respectively. In each study, the participants were divided into three test groups, separated by where they were asked to place their phone during the experiment.
- Pocket or bag
- Other room
Participants in all three test conditions were then given two tasks: one that measured their ability to track information while completing difficult tasks (working memory), and another that measured their ability to understand and solve new problems (fluid intelligence). They were then asked to answer a series of questions about their beliefs about their performance in the tasks, and their beliefs about their phones.
Some of the findings from the report are summarized below:
- For both tasks, participants in the “Other room” category did better than those in the “Pocket/bag” category, who did better than those in the “Desk” category. See a graph of the means here. This suggests that the closer participants were to their smartphones, the more their abilities were impacted.
- Most participants reported that they did not consciously think of their phones in any location during the experiment. This supports the hypothesis that smartphones adversely affect cognitive abilities even when their owners aren’t thinking of them consciously.
- Participants were unaware of the effects of their phones on their cognitive abilities. When asked how much their phones typically affected their performance during the experiment and in general, a majority of participants believed that there was no effect.
- The more dependent a participant was on their phone, the more their cognitive abilities were effected. The experiment conductors asked participants to self-evaluate their phone dependence by rating statements like “I would have trouble getting through a normal day without my cellphone.”
Rats and Variable Rewards
None of this is particularly surprising. In his 2016 book The Attention Merchants, author Tim Wu – an influential lawyer who earlier coined the phrase net neutrality – drew a parallel between smartphones and a series of experiments done in the 1960s by psychologist B.F. Skinner . In Skinner’s experiments, rats were given rewards in the form of food whenever they pressed a lever in their cage. However, if the animals received food inconsistently, rather than every time they pressed, Skinner found that they would press far more frequently than if the reward was consistent.
This strategy, called the variable reward ratio in the study of operant conditioning, is one that casinos and other gambling settings frequently exploit. “Occasional but unpredictable payoffs” occur, eliciting compulsive behaviour from the subjects. 
Wu compared our compulsions to check our phones frequently to the rats’ compulsions to press their levers. Instead of food, our rewards are the social reactions from our followers (likes, reactions, hearts) and new morsels of information from our friends and coworkers (texts, comments, emails).
Remarkably, Skinner’s studies found that when the rats stopped receiving rewards at all after they pressed on the levers, they eventually stopped pressing. “The behavior is said to have been extinguished.” 
Reducing the Detrimental Effects
These findings give us some compelling reasons to decondition ourselves from checking our phones. Here are a number of steps you can take to limit the negative effects of your device.
1. Do Not Disturb
Keep your phone on DND. It seems simple, but if you’re used to being at the beck and call of your phone, it’ll make a remarkable difference. If you’re waiting for an urgent message or call, temporarily take it off DND. The idea is to reduce your dependence on your device, which seems to limit its adverse effects to your mental capacities.
2. Airplane Mode
This guarantees that even if you pick up your phone by accident, there will be no shiny notifications to entice you. This further emancipates you from your phone. I’ve found this to be effective in breaking my habit of compulsively checking my notifications, because I’ve come to expect none.
3. Hide Your Phone
Place your phone somewhere that is out of your direct and peripheral field of vision, and preferably in another room.
4. Uninstall Unnecessary Apps
Be ruthless about what you consider a necessary app. A mentor of mine – who happens to be the CEO of her company – told me that she uninstalled Slack and other work-related apps every Friday, and reinstalled them on Monday mornings. You can do the same for other distracting apps.
5. Selective Notification Switches
You can always selectively toggle notifications for any app on your phone through the Settings app on the device. This is recommended over switching them off for each app individually, because apps may limit the duration they allow you to keep their notifications off. For example, Facebook Messenger only gives you up to 24 hours of notification silence through their app.
Smartphones have added a lot of value to our lives. They’ve also posed interesting issues to us in being attention demanding and anti-productive devices. As we collectively grow more dependent on our phones, some influential folks are urging us to distance ourselves from the devices – or at least educate ourselves on their impacts.
- The study referenced in this article, from the Journal of the Association for Consumer Research.
- Tristan Harris, founder of the Center for Humane Technology. [Medium]
- Tim Wu, author of The Attention Merchants [Amazon] and The Master Switch [Amazon].
- Arianna Huffington, of The Huffington Post and Thrive Global, on setting tech boundaries.
- Joshua Fields Millburn and Ryan Nicodemus, creators of the site and film The Minimalists, on digital decluttering.
- Tim Ferriss, author of The 4-Hour Workweek, on taking social media breaks.