Furthermore, even when not using the Internet for any specific purpose, smartphones have introduced widespread and habitual “checking” behaviours, characterized by quick but frequent inspections of the device for incoming information from news, social media, or personal contacts 18 . These habits are thought to be the result of behavioural reinforcement from “information rewards” that are received immediately on checking the device 19 , potentially engaging the cortico‐striatal dopaminergic system due to their readily available nature 20 . The variable‐ratio reinforcement schedule inherent to device checking may further perpetuate these compulsive behaviours 21 .

Multiple factors are driving the rapid uptake and extensive usage of Internet‐enabled technologies across the globe. This is partly due to the Internet now being unavoidable, ubiquitous, and a highly functional aspect of modern living. For instance, Internet use is now deeply entwined with education, travel, socializing, commerce, and the majority of workplaces. Along with pragmatic uses, the Internet also offers an endless array of recreational and entertainment activities, through podcasts, e‐books, videos, streaming movies and gaming. However, the ability of the Internet to capture and hold attention is not solely due to the quality of media content available online. Rather, it is also driven by the underlying design and presentation of the online world. One such example is the self‐evolving “attraction mechanism”; whereby aspects of the Internet that fail to gain attention are quickly drowned out in the sea of incoming information, while the successful aspects of the adverts, articles, apps or anything that does manage to capture our attention (even superficially) are logged (through clicks and scrolls), noticed (through online shares), and subsequently proliferated and expanded upon. Alongside this, leading technology companies have been accused of intentionally capitalizing on the addictive potential of Internet, by studying, testing, and refining the attention‐grabbing aspects of their websites and applications (“apps”) to promote extremely high levels of engagement, without due concern for user well‐being 17 .

The Internet consumes a considerable chunk of our attention on a day‐to‐day basis. The vast majority of adults go online daily, and over a quarter report being online “almost constantly” 2 . Within this, one in five American adults are now “smartphone‐only” Internet users 1 . Importantly, the introduction of these Internet‐enabled mobile devices has also reduced the “digital divide” previously experienced by lower and middle income countries 15 . The amount and frequency of Internet usage is even more pronounced amongst younger people. Most adults today witnessed the beginning of the transition from “Internet‐free” to “Internet‐everywhere” societies. However, younger generations (termed “digital natives” 16 ) have been brought up entirely within a “connected world” , particularly in developed countries. Consequently, digital natives are often the first to adopt new online technologies as they arise 16 , and engage extensively with all existing features of the Internet. For instance, 95% of US teens have access to a smartphone, and 45% are online “almost constantly” 3 .

Cognitive consequences of the attention‐grabbing Internet

The unprecedented potential of the Internet to capture our attention presents an urgent need for understanding the impact that this may have on our thought processes and well‐being. Already, education providers are beginning to perceive detrimental effects of the Internet on children's attention, with over 85% of teachers endorsing the statement that “today's digital technologies are creating an easily distracted generation”22. The primary hypothesis on how the Internet affects our attentional capacities is through hyperlinks, notifications, and prompts providing a limitless stream of different forms of digital media, thus encouraging us to interact with multiple inputs simultaneously, but only on a shallow level, in a behavioural pattern termed “media multi‐tasking”23, 24.

The seminal study by Ophir et al23 was among the first to explore the sustained impact of media multi‐tasking on cognitive capacities. This was a cross‐sectional study of individuals who engaged in “heavy” (i.e., frequent and extensive) media multi‐tasking compared to those who did not. Cognitive testing of the two groups produced the then‐surprising finding that those involved in heavy media multi‐tasking performed worse in task‐switching tests than their counterparts – contrary to the authors’ expectation that the “extra practice” afforded by frequent media multi‐tasking would confer cognitive benefit in task‐switching scenarios. Closer inspection of findings suggested that the impeded task‐switching ability in heavy media multi‐tasking individuals was due to their increased susceptibility to distraction from irrelevant environmental stimuli23.

Since these initial findings, the effects of media multi‐tasking on cognition have come under increasing scrutiny, because the increasingly diverse forms of entertainment and activities available through the online world can further our capabilities (and temptation) of engaging in media multi‐tasking25, even on single devices. For instance, Yeykelis et al26 measured participants’ media multi‐tasking between different types of online media content while using just one device (personal laptops), and found that switches occurred as frequently as every 19 seconds, with 75% of all on‐screen content being viewed for less than one minute. Measures of skin conductance during the study found that arousal increased in the seconds leading up to media switching, reaching a high point at the moment of the switch, followed by a decline afterward26. Again, this suggests that the proclivity for alternating between different computer windows, opening new hyperlinks, and performing new searches could be driven by the readily available nature of the informational rewards, which are potentially awaiting in the unattended media stream. Supporting this, the study also found that, whereas switching from work‐related content to entertainment was associated with increased arousal in anticipation of the switch, there was no anticipatory arousal spike associated with entertainment to work‐content switches26.

The growing concern around the increasing amount of media multi‐tasking with the spread of ubiquitous Internet access has resulted in further empirical studies. These have produced conflicting findings, with some failing to find any adverse effects on attention27, and others indicating that media multi‐tasking may even be linked to increased performance for other aspects of cognition, such as multisensory integration28. Nonetheless the literature, on balance, does seem to indicate that those who engage in frequent and extensive media multi‐tasking in their day‐to‐day lives perform worse in various cognitive tasks than those who do not, particularly for sustained attention25.

Imaging studies have shed light onto the neural differences which may account for these cognitive deficits. Functionally, those who engage in heavy media multi‐tasking perform poorer in distracted attention tasks, even though exhibiting greater activity in right prefrontal regions29. As right prefrontal regions are typically activated in response to distractor stimuli, the observed increases in recruitment of these regions alongside poorer performance suggests that heavy media multi‐taskers require greater cognitive effort to maintain concentration when faced with distractor stimuli29. Structurally, high levels of Internet usage30 and heavy media multi‐tasking31 are associated with decreased grey matter in prefrontal regions associated with maintaining goals in face of distraction (such as the right frontal pole and anterior cingulate cortex). However, the findings to date must be interpreted with caution, as various confounding factors may be affecting the results of these cross‐sectional imaging studies. Although the differences persist when controlling for general digital media use and other simple confounders (age, gender, etc.), further research is required to examine if the observed neural differences are specifically attributable to heavy vs. light media multi‐tasking, or in fact driven by broader differences in lifestyle between the two groups.

Given the amount of time that people now spend in media multi‐tasking via personal digital devices, it is increasingly relevant to consider not only sustained changes which arise in those who engage in large amounts of media multi‐tasking, but also the acute effects on immediate cognitive capacities. A meta‐analysis of 41 studies showed that engaging in multi‐tasking was associated with significantly poorer overall cognitive performance, with a moderate‐to‐large effect size (Cohen's d=–0.71, 95% CI: –0.86 to –0.57). This has been confirmed by more recent studies, further showing that even short‐term engagement with an extensively hyperlinked online environment (i.e., online shopping for 15 minutes) reduces attentional scope for a sustained duration after coming offline, whereas reading a magazine does not produce these deficits32.

Overall, the available evidence strongly indicates that engaging in multi‐tasking via digital media does not improve our multi‐tasking performance in other settings – and in fact seems to decrease this cognitive capacity through reducing our ability to ignore incoming distractions. Much of the multi‐tasking investigations so far have been focusing on personal computers. However, smartphone technologies may even further encourage people to engage in media multi‐tasking through high rates of incoming prompts from emails, direct messages and social media notifications occurring while both using and not using the device. Thus, along with determining long‐term consequences of media multi‐tasking, future research should examine how the constant multi‐tasking made possible by Internet‐enabled mobile devices may impact daily functioning through acute but high frequency effects.

Furthermore, both the immediate and chronic effects of media multi‐tasking are relatively unexplored in children and adolescents, who are the prime users of such technologies33 and are at a phase of development that is crucial for refining higher cognitive abilities14. The first longitudinal study of media multi‐tasking in young people has recently found that frequent multi‐tasking behaviours do predict the development of attentional deficits specifically in early adolescents, but not in older teens34. Additionally, extensive media multi‐tasking during childhood and adolescence could also negatively impact cognitive development through indirect means, by reducing engagement with academic and social activities, as well as by interfering with sleep35, or reducing the opportunity to engage in creative thinking36, 37. Clearly, further research is necessary to properly measure the effects of ubiquitous computing on children's cognitive development, and to find practical ways for ameliorating any detrimental impact this may be having.