You’ve been waiting two months to get time on your boss’s calendar. Between travel, meetings, and last-minute cancellations, your one-on-one keeps getting bumped. Now, finally, you have thirty minutes to pitch the idea you’ve been working on for weeks. Knowing their style, you build a short, focused presentation: five slides, clean bullets, the key ask up front. You even rehearse aloud—once to your dog, twice in the mirror—so you can keep it tight.

The meeting starts on time, and your boss smiles as they join the video call. “Excited to hear what you’ve got for me,” they say. “Let’s dive in.” You share your screen and begin the pitch.

But less than a minute in, you notice your boss’s eyes flick downward—then linger. Their hands move slightly out of frame. It’s subtle, but unmistakable: they’re checking their phone.

You pause. “Do you need a minute before I continue?”

“No, I’m listening,” they reply, without looking up. “Please, go ahead.”

So you do. You keep your pace, walk through the slides, and make your final ask. When you stop sharing your screen, there is a beat of silence. Then your boss looks up and asks, “How much is this going to cost?”

You feel disappointed. That information was clearly presented on slide two.

Your boss missed that key detail because of their divided attention: they were trying to juggle listening to your pitch while checking their phone, but ended up not fully processing either. Even though they were physically present and responded in the moment, their cognitive resources were split and reduced.

Our brain’s ability to process multiple streams of information at once is limited. When we try to focus on more than one thing, our performance on both tasks tends to drop. In high-stakes settings, even a brief lapse in attention can lead to trouble. 

In other words, multitasking doesn’t work—at least not well. Understanding the limits of divided attention helps explain why knocking out a couple of things at once is rarely as effective as it seems, and why fully focusing on one task at a time is sometimes a better choice.

Multitasking: Performing more than one task at the same time. In practice, multitasking usually means switching rapidly between tasks, which can slow us down and increase errors.

Capacity Theory: A model of attention introduced by Daniel Kahneman that describes attention as a limited mental resource. According to this theory, we can divide our attention across tasks, but doing so reduces the available resources for each, leading to performance drops when tasks compete for that limited capacity.

Cognitive Load: The total amount of mental effort used in working memory. When cognitive load becomes too high—such as when we try to multitask or process complex information—our performance often declines.

Frontoparietal Control Network: A network in the brain that helps us manage attention, switch between tasks, and stay focused. It becomes more active when we attempt to multitask, signaling increased cognitive demand.

Phubbing: A blend of “phone” and “snubbing,” this term describes the act of looking at your phone while, or instead of, engaging with the person you're with.

Vigilance: The ability to maintain attention and remain alert over long periods of time, especially when monitoring for rare or subtle signals. Research on vigilance began with Norman Mackworth’s Clock Test, which demonstrated how performance declines over time during sustained attention tasks.

From an evolutionary standpoint, our brains didn’t evolve to multitask. Early humans were much more likely to survive if they focused on one thing at a time, such as watching for predators. Dividing attention between multiple complex tasks wasn’t something we needed to do often. Even though we now live in a world that constantly demands multitasking, our attention systems are still wired for depth, not breadth.

The formal study of how we split our focus really took off in the 1940s, during and after World War II. At the time, psychologist Norman Mackworth was trying to understand the limits of vigilance—how pilots, radio operators, and radar technicians could manage multiple inputs under pressure. In his famous Clock Test, participants watched a slowly moving hand on a clock-like device and had to detect occasional jumps. Mackworth found that detection performance dropped sharply after just 30 minutes, revealing how quickly sustained attention can degrade under monotony and divided demands.² The stakes were high, and the brain’s limits became clear.

Around the same time, British psychologist Colin Cherry was exploring how we process competing sounds. In 1953, he developed the dichotic listening task, where participants wore headphones and received different audio streams in each ear. They were asked to focus on and repeat one message while ignoring the other. Cherry found that while participants could successfully repeat the attended message, they often failed to notice major changes in the unattended one, such as a switch in language or a voice change.³ These findings raised important questions: If two messages enter our ears at the same time, why do we only process one? And what happens when we try to divide attention between them?

In 1958, psychologist Donald Broadbent introduced one of the first major theories of attention. He suggested that our brains work like a filter, letting some information through while blocking the rest.⁴ That early research focused more on selective attention—when we are able to tune out distractions to focus on one thing—but it laid the foundation for understanding what happens when we try to divide our attention across multiple tasks.

A few years later, Daniel Kahneman—who would go on to win the Nobel Prize in Economics—published Attention and Effort, where he introduced capacity theory.¹ He described attention as a limited mental resource that we can spread across different tasks, but with clear trade-offs. According to Kahneman, we can spread that resource to focus on different tasks, but the more we divide it, the less we have to give to any one thing. That idea still shapes how we understand multitasking today.

As our world grew more complex, researchers began using lab experiments and brain imaging to explore how multitasking affects the brain. fMRI studies have shown that when we try to juggle multiple tasks—especially ones that require concentration—our brains call on areas responsible for managing focus and switching between activities. One of the most important of these is the frontoparietal control network, a system that acts like a mental traffic controller: it helps us decide what to pay attention to and when to shift gears.⁵ When we divide our attention, this system ramps up its activity. But that extra effort comes at a cost: slower performance, more mistakes, and greater mental fatigue. Knowing the limits of our attention is half the battle to keeping our focus where it counts.

Norman Mackworth
A British psychologist best known for his work on vigilance during World War II. His Clock Test demonstrated that sustained attention drops over time, laying the foundation for understanding the limits of focus under pressure.

Colin Cherry
A pioneer in auditory attention research, his 1953 dichotic listening experiments showed that when people are exposed to two audio streams at once, they process only one effectively.

Donald Broadbent
An early theorist of attention who proposed the Filter Model in 1958. His work explained how our brains prioritize certain inputs while ignoring others, shaping how psychologists approached multitasking and divided attention.

Daniel Kahneman
Renowned for his work on decision-making and behavioral economics, Kahneman introduced Capacity Theory in his 1973 book Attention and Effort. He framed attention as a limited mental resource that can be divided across tasks, but with clear costs. His work continues to influence how we think about cognitive effort and multitasking today.

When we think we’re capable of doing it all, we may not end up doing any of it well. Divided attention is distracted attention, and the impacts can range from everyday frustrations, like missed details or strained conversations, to serious consequences, including workplace errors and life-threatening accidents.

Phubbing and deteriorated relationships

Splitting attention during conversations weakens interpersonal connection. When our attention is divided and we aren’t fully present, we can miss emotional cues, respond off-target, or forget what was just said. Checking a phone mid-conversation—whether to scroll, reply, or clear a notification—signals disinterest. Over time, those signals accumulate in unhealthy ways.

In a survey of 453 adults, 46.3% reported being phubbed by their romantic partner, and 22.6% said it led to conflict, with more frequent phubbing linked to lower relationship satisfaction.6 The study, published in 2016, reported participants feeling excluded, ignored, and emotionally disconnected when their partners prioritized phones during interactions.

Children are affected by phubbing too. In a 2022 study of nearly 1,000 mothers and preschool to kindergarten-aged children, researchers found that when mothers were phubbing, there was a significant association with children’s emotional and behavioral problems.⁷ The weaker the mother–child attachment, the stronger the link between phubbing and those emotional challenges. Even in early childhood, children are sensitive to the absence of focused attention, and repeated disengagement can disrupt emotional development and attachment patterns.

Moments of partial presence resulting from divided attention can leave lasting impressions on partners, on children, and on the emotional tone of our closest relationships.

Work performance and accuracy

Multitasking is common in the workplace. Many of us answer emails during meetings, respond to messages while finishing reports, and switch between tabs and tasks throughout the day. But dividing attention across the demands of work reduces our accuracy, slows our performance, and increases the likelihood we’ll miss something important.

In 2019, researchers found that dividing attention activates executive control systems in the brain, particularly the frontoparietal control network, involved in focus, decision-making, and controlling attention.⁵ This requires additional cognitive effort, which increases cognitive load and reduces available working memory. As a result, task-switching can impair our performance, elevate our fatigue, and interfere with our ability to retain or prioritize information. 

In high-risk environments like healthcare, multitasking is encouraged and planned for with training.⁸ But divided attention can lead to serious consequences. In one observational study, doctors experienced an average of 9.4 interruptions per hour while prescribing medication, and both interruptions and multitasking were associated with an increase in prescribing errors.⁹ The likelihood of error was even greater when physicians were fatigued or showed lower working memory capacity.

At the office, even small shifts in attention, such as glancing at a Slack notification or briefly switching applications between Zoom and email, can interrupt processing and lead to lower-quality work. To make a workload more manageable, carving out focus time and closing out other apps is the real key to success.

Texting while driving

Driving requires full attention. Each moment involves scanning the road, adjusting to changes, and reacting quickly to hazards. Texting while driving divides and pulls our attention in multiple directions. It engages the eyes, hands, and mind all at once, which significantly increases the risk of a crash.

In a study by the Federal Motor Carrier Safety Administration (FMCSA), texting while driving was associated with a crash or near-crash event 23.2 times more often than driving without distractions.¹⁰ The researchers found that drivers took their eyes off the forward roadway for an average of 4.6 seconds while texting. At 55 miles per hour, that’s enough time to travel the length of a football field without looking.

Even voice-to-text systems, often thought to be safer, still impose substantial cognitive and visual demands on our attention. A Texas A&M Transportation Institute study with 43 drivers showed that both manual texting and voice-to-text caused reaction times to double, and forward roadway gaze time decreased significantly, with Siri and Vlingo, performing on par with manual texting.¹¹ Even worse, the drivers reported feeling safer when using their voice-to-text apps. These findings underline a clear reality: whether physically handling or verbally dictating a phone, dividing attention at the wheel undermines safety for drivers and everyone around them.

Divided attention is a complex issue, and we’re only beginning to understand the brain mechanics of it. Researchers, educators, and employers continue to debate how attention works across different contexts, and whether some kinds of multitasking are more acceptable—or even beneficial—than others. From task switching in high-pressure jobs to media multitasking and cultural differences, not everyone agrees on where the limits lie or how we should interpret the evidence.

Task switching vs. multitasking

One of the biggest debates in the science of attention is whether humans can truly multitask, or if we're really just switching rapidly between tasks. This distinction matters because task switching carries hidden costs. Every time we shift our focus, we need to mentally “reset,” and that takes time and energy. Even short delays can reduce accuracy and increase error rates.

In emergency medicine, for example, physicians often think they are multitasking. But observational research in emergency departments shows that what looks like multitasking is actually rapid task switching, with each shift increasing the likelihood of missed information or mistakes. A study published in Annals of Emergency Medicine found that even experienced clinicians showed performance declines during frequent switches, especially in high-stakes environments with competing demands.¹²

In workplaces, multitasking is commonly seen as efficient and prized as a trait of high-performing employees, but research tells a different story. Kahneman’s capacity theory and neuroimaging data both support the idea that attention is a finite resource.^1,5 When we try to do multiple cognitively demanding tasks at once, we’re not amplifying or multiplying our attention—we’re dividing and depleting it. The more we switch, the more performance drops.

Can some people handle media multitasking better than others?

The explosion of digital technology has made media multitasking, like watching TV while scrolling social media, common across all age groups. Some researchers have suggested that younger generations (sometimes called “digital natives”) are adapting, developing cognitive strategies that could possibly help them manage multiple media streams more effectively than older adults.¹³

However, Ophir, Nass, and Wagner’s 2009 study found that heavy media multitaskers actually performed worse than light multitaskers on tasks requiring working memory, sustained attention, and task switching.¹⁴ The researchers assessed participants using a series of computerized tests that measured their ability to filter distractions, manage competing information streams, and switch between tasks efficiently. Despite their confidence, high media multitaskers showed more distractibility and less cognitive control. Critics of this view have pointed out that results vary across experiments and that task design and motivation may influence outcomes.¹⁵ The consensus remains that while some individuals report feeling more productive, there’s little evidence that media multitasking improves cognitive performance.

Cultural attitudes toward divided attention

Some cross-cultural studies suggest that individuals in certain societies may develop different attentional habits based on social and environmental context. For example, research has shown that East-Asian participants tend to focus more on context and background elements in visual scenes, while Western participants focus more narrowly on central or foreground objects.¹⁶ In the study, participants from Japan and the United States watched short animated clips of underwater activity and were later asked to describe what they saw. Japanese participants were 70% more likely to mention background items, such as the water, plants, and how the fish were moving together. American participants, on the other hand, mostly focused on the biggest or most noticeable fish, even naming details such as it looking like a trout. The researchers suggested that these differences may reflect deeper cultural habits—some cultures pay more attention to the overall setting and relationships, while others focus more on standout details. These habits might be shaped by the way different societies have learned to see the world over time.

Some researchers have pushed back on this idea, saying it confuses how we see the world with how we divide our attention.¹⁷ While it’s clear that people from different cultures may focus on different parts of a scene, there’s no strong evidence that one group is actually better at multitasking. Education and daily routines might shape our habits, but they don’t change the basic limits of how much attention our brains can handle. The debate continues in cultural psychology circles, especially regarding how these findings should—or shouldn’t—be applied to education and work environments.

The “Textalyzer” debate in New York

In 2017, New York lawmakers proposed a controversial bill to allow police officers to use a “textalyzer”—a device that could scan a driver’s phone after a crash to determine whether it had been in use.¹⁸ The legislation emerged in response to a growing number of fatal crashes where distracted driving was suspected but hard to prove, since phone data is typically protected and not released without a court order.

The push for the bill was led by Ben Lieberman, whose 19-year-old son Evan was killed in a 2011 car crash. Through civil litigation, Lieberman discovered that the driver had been texting at the time of the crash—information not made available during the initial police investigation. Frustrated by the lack of tools to hold distracted drivers accountable, Lieberman began campaigning for stronger policies and public awareness, arguing that distracted driving was becoming the new DUI.

While the bill wasn’t passed, the case raised public awareness and sparked national debate—not only about digital privacy and civil liberties, but about the real consequences of divided attention behind the wheel. It exposed how difficult it can be to measure distraction in real time, and how few enforcement mechanisms exist for this widespread risk. The Textalyzer controversy underscored an uncomfortable truth that the cost of divided attention can be fatal, and the systems we have aren’t always built to track it.

Fatal flight over Lake Eildon

In 2004, a private flight over Lake Eildon in Victoria, Australia, ended in tragedy when a Piper PA-28R aircraft struck a power cable approximately 133 feet above the water. The collision with the wire and the subsequent crash into the lake killed the pilot and all three passengers. Investigators found no evidence of environmental, mechanical, or operational failure. Instead, they blamed it on distracted attention.

A video camera recovered from the wreckage revealed that the aircraft had been flying unusually low, with the front-seat passenger filming houseboats as the plane passed overhead.¹⁹ The pilot, who may have been adjusting flight altitude to accommodate the filming or simply engaged in sightseeing alongside the passengers, appears to have been unaware of the hazard ahead. According to the coroner’s findings, this focus on the lake scenery likely drew the pilot’s attention away from altitude monitoring and terrain awareness, resulting in a fatal descent into the power line.

This case illustrates a core challenge of divided attention: when we try to manage more than one cognitive demand—even voluntarily—our ability to safely perform a primary task can degrade without warning. The pilot was not interrupted, nor forced to shift focus. The distraction was self-imposed by the pilot attempting to focus on too many things at once.

In aviation and other safety-critical professions, divided attention can’t always be attributed to sudden overload. Sometimes, it stems from competing priorities that don’t seem risky at the time. But as this crash tragically demonstrated, small lapses or redirects of our attention can reduce our ability to do something critically important.

Selective Attention

If divided attention shows us the cost of doing too much at once, selective attention offers a way back to focus. Learn how the brain filters information, and how to make that filter work in your favor.

Attentional Bias

Want the full picture on how attention works, what grabs it, what holds it, and what pulls it away? Dive into this comprehensive guide on attention to understand the cognitive system that shapes every moment of focus.

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