Research Shows Multitasking Slows Reaction Time and Hurts Memory for 97.5% of People
Here’s the finding that tends to stop people cold: the more confident someone is in their multitasking ability, the worse they typically perform on multitasking tests. A 2009 Stanford study by Ophir, Nass and Wagner, published in Proceedings of the National Academy of Sciences, found that heavy media multitaskers were more easily distracted, worse at filtering irrelevant information and slower at switching between tasks than people who rarely multitasked.
The people most certain they had the skill were the ones who least demonstrated it. If that sounds like it might describe you, the rest of the science is worth understanding.
Why Almost Nobody Can Actually Multitask
The foundational number comes from a 2010 study by Jason Watson and David Strayer published in Psychonomic Bulletin and Review. Two hundred participants were placed in a high-fidelity driving simulator and asked to perform a second cognitively demanding task at the same time. Only 2.5% showed no measurable performance loss.
Watson and Strayer called them supertaskers. For everyone else, braking reaction times slowed by 20%, following distances grew by 30%, memory performance dropped 11% and math accuracy fell 3%.
The key word is “measurable.” Most participants didn’t feel the decline. They kept going, confident they were managing fine. That subjective sense of competence is precisely what makes the myth so durable.
What Makes Supertaskers Different at a Neural Level
A follow-on neuroimaging study by Medeiros-Ward, Watson and Strayer, also in Psychonomic Bulletin and Review, found that supertaskers show reduced prefrontal cortex activation during dual tasks compared to regular participants. Their brains aren’t working harder — they’re working more efficiently.
That finding matters because it shifts supertasking from a skill to a trait. The neural efficiency supertaskers show doesn’t appear to be trainable. You either have it or you don’t, and the 2.5% figure suggests almost everyone reading this does not.
The Switch Cost Problem Nobody Talks About
For the 97.5% who aren’t supertaskers, what feels like multitasking is actually rapid task-switching. The brain shifts attention, reorients to the new task and resumes — repeatedly, across the day. Each shift carries what researchers call a switch cost.
The American Psychological Association’s review of task-switching research estimates those costs reduce effective productivity by up to 40% on complex work. That’s not a rounding error. That’s potentially two days out of every five disappearing into the cognitive overhead of changing focus.
UC Irvine informatics professor Gloria Mark, whose field research is detailed in her 2023 book Attention Span, measured a related cost: after a single interruption, it takes an average of 23 minutes and 15 seconds to fully regain focus on the original task. In a workday structured around open inboxes and Slack notifications, that tax compounds continuously.
The Difference Between Distraction and Multitasking
These two things get conflated constantly and they’re not the same. True multitasking is something almost nobody can do. Habitual context-switching driven by notifications, open tabs and always-on communication tools is something almost everybody does. One is a rare neurological trait. The other is a learned behavior reinforced over years of working in distraction-saturated environments.
That distinction matters because the learned version is reversible. Distraction habits that developed over years of fragmented work can be unwound through deliberate structure — and the research points consistently toward the same mechanism for doing it.
How to Recover the Productivity Switch Costs Are Taking
Protected single-task blocks are the most evidence-supported structural fix available. A 90-minute window with notifications off, one defined output and a hard stopping point directly counters both the switch-cost problem and the distraction habit at the same time.
Most people who try it report two things: they get significantly more done, and the work feels qualitatively different. That second part is the tell. When focus isn’t being interrupted every few minutes, the brain can actually build on what it was just doing rather than constantly restarting. The research on switch costs explains why. The experience of a single protected block tends to confirm it.
The question worth sitting with isn’t whether you’re a supertasker. It almost certainly isn’t whether you’re in the 2.5%. It’s how many hours of your week are currently being absorbed by switch costs you can’t feel — and what one less distracted day might actually produce.
This article was created by content specialists using various tools, including AI.
