What Does the Research Say About Multitasking?
Written By Aftertone Team
Thursday, May 14, 2026
15 min read
What Does the Research Say About Multitasking?
The research on multitasking shows that genuine simultaneous multitasking on cognitive tasks is not possible for human beings. What people experience as multitasking is rapid task switching: the brain alternating between tasks, spending a brief period on each, rather than performing them simultaneously. This switching produces measurable costs in accuracy, speed, and quality on both tasks. The research is among the most consistent findings in cognitive psychology and has been replicated across multiple paradigms and populations.
What Rubinstein, Meyer, and Evans found (2001)
Joshua Rubinstein, David Meyer, and Jeffrey Evans published research in 2001 in the Journal of Experimental Psychology: Human Perception and Performance showing that task switching produces measurable performance costs. Their research identified two components of switching cost: goal shifting (time to switch mental goals from one task to another) and rule activation (time to suppress the rules of the prior task and activate the rules of the new task). Both components contributed to the overall switching cost.
The magnitude of the cost depended on task complexity: for simple tasks, switching costs were relatively small. For complex tasks requiring different cognitive rule sets (like switching between mathematical operations and word tasks), switching costs could consume up to 40% of productive time. This 40% figure is the most cited from their research. It represents the worst-case switching cost for highly dissimilar complex tasks, not the average across all switching types.
Why multitasking feels productive
The subjective experience of multitasking is often one of high productivity: many things being done simultaneously, rapid responses to multiple demands, constant activity. This feeling is largely disconnected from actual output quality. Research by David Strayer and colleagues found that heavy multitaskers had significantly worse performance on task-switching and filtering tasks than light multitaskers, despite reporting that they were better at multitasking. The people who multitask most are the worst at it, and are the most overconfident about their ability to do it.
The productivity feeling comes from the responsiveness component: rapid switching between tasks feels like handling many things simultaneously. But the output of each task in a heavy-switching session is produced at degraded quality compared to the same tasks done sequentially with full attention. The feeling tracks the switching frequency rather than the output quality.
Media multitasking research
Clifford Nass, Eyal Ophir, and Anthony Wagner's 2009 Stanford study compared heavy media multitaskers (people who frequently use multiple media simultaneously) with light media multitaskers on a series of cognitive tasks. The heavy multitaskers performed significantly worse on tasks measuring attention filtering (ignoring irrelevant stimuli), task switching speed, and working memory. They were more susceptible to distraction from irrelevant environmental stimuli and had larger switching costs.
The Nass study raised a question the research has been working on since: does frequent media multitasking cause these deficits, or do people with pre-existing attentional difficulties seek out more stimulation through media multitasking? Longitudinal research has found some evidence for both directions. The causal picture is not fully settled, but the cross-sectional association between heavy media multitasking and poorer attentional control is consistent.
The illusion of supertaskers
David Strayer and Jason Watson's research on "supertaskers" identified that approximately 2.5% of the population can perform two cognitive tasks simultaneously without the performance costs that affect everyone else. These rare individuals (Strayer and Watson specifically studied dual-task performance while driving) showed no significant degradation in either task during simultaneous performance. Their research attracted attention because it provided evidence that genuine multitasking is not universally impossible, just nearly so.
The important context: 97.5% of people are not supertaskers. For the overwhelming majority of knowledge workers, the switching cost research applies in full. And the supertasker research was conducted in a specific paradigm (driving plus a cognitive task) rather than across general knowledge work. The existence of 2.5% supertaskers does not meaningfully change the practical recommendation for the other 97.5%.
Practically useful conclusions
The research consistently supports single-tasking as more productive than multitasking for cognitively demanding work. Sequential task completion (completing one task before beginning the next) produces better total output quality than time-divided multitasking. Minimising the number of context switches in a working session reduces the accumulated switching cost. The context switching cost research and the multitasking research together provide the scientific basis for focus blocks, distraction elimination, and single-task work interfaces.
What the research does and does not show
The research clearly shows that genuine simultaneous multitasking on cognitive tasks is not possible for approximately 97.5% of people, that task switching produces measurable performance costs on both tasks (Rubinstein, Meyer, and Evans (2001)), that heavy media multitaskers perform worse on attentional filtering and task-switching tests than light multitaskers (Nass, Ophir, and Wagner (2009)), and that the subjective sense of multitasking productivity is disconnected from actual output quality.
The research does not show that all task switching is equally costly. Rubinstein et al.'s 40% productivity cost figure is specific to switching between highly dissimilar complex tasks. Switching between closely related tasks, switching at natural stopping points, and switching between low-demand tasks carries significantly smaller costs. The 40% figure is the upper bound of switching cost, not the average across all switching types.
The research also does not show that heavy media multitasking definitively causes attentional deficits. Nass et al.'s 2009 study is cross-sectional: it shows heavy media multitaskers have worse attentional control, but cannot establish whether the multitasking caused the deficits or whether people with pre-existing attentional difficulties seek out more stimulation through media multitasking. Longitudinal research has found evidence in both directions. The causal direction is not fully settled, though the association is consistent and the practical recommendation — reduce switching — is supported regardless of causal direction.
Aftertone's planned versus actual report makes the multitasking cost concrete: comparing output on days with high context-switching (many short tasks, frequent communication, reactive work) versus days with protected focus blocks shows the productivity differential that Rubinstein and colleagues' research predicts. Most users who track this find the gap is larger than they expected.
Frequently asked questions
Is multitasking actually impossible?
Genuine simultaneous multitasking on cognitive tasks is not possible for approximately 97.5% of people. What people experience as multitasking is rapid task switching: the brain alternating between tasks rather than performing them simultaneously. Rubinstein, Meyer, and Evans (2001) found this switching produces measurable costs in accuracy, speed, and quality on both tasks. A small percentage of people (Strayer and Watson's 'supertaskers') can perform some task combinations without cost, but the overwhelming majority of knowledge workers experience the full switching cost.
How much does multitasking reduce productivity?
Rubinstein, Meyer, and Evans found switching costs of up to 40% of productive time for highly dissimilar complex tasks. This is the upper bound for the worst-case switching type, not the average across all task switching. More routine switching produces smaller costs. The cumulative effect across a day of frequent switching between dissimilar tasks can be substantial, consistent with the gap between planned and actual output that most knowledge workers experience.
Are heavy multitaskers better at multitasking?
Heavy multitaskers are not better at multitasking — they are worse. Strayer and colleagues found heavy multitaskers perform significantly worse on attentional filtering and task-switching tasks than light multitaskers, despite reporting higher confidence in their multitasking ability. The people who multitask most are the most overconfident about it and the worst at it. Frequent multitasking does not appear to build the skill; it may degrade the attentional capacities that single-tasking requires.
What is the research on media multitasking?
Nass, Ophir, and Wagner's 2009 Stanford study found heavy media multitaskers performed significantly worse on attentional filtering, task switching, and working memory tasks compared to light multitaskers. They were more distracted by irrelevant stimuli and had larger switching costs. Whether the deficits cause heavy media use or heavy media use causes the deficits is not fully settled; the association between heavy media multitasking and poorer attentional control is consistent.
What should I do differently based on multitasking research?
Work on one task at a time during focused work sessions. Close unrelated applications and browser tabs. Minimise context switches by completing tasks before switching to new ones. Cluster similar tasks together to reduce the cognitive rule-switching that produces the highest switching costs. Batch communications (email, messages) into specific windows rather than responding throughout the day, converting reactive multitasking into sequential task completion.
