Heavy multitasking gets treated as a skill, something people get better at with practice. A well-known Stanford study set out to test exactly that assumption, and the results ran the opposite direction.
The Study
Researchers at Stanford, published in PNAS, compared people who frequently juggle multiple streams of media (texting, browsing, watching, listening, all at once) against people who rarely do. The hypothesis going in was that heavy multitaskers would show an advantage at filtering information and switching between tasks, since that's effectively what they practice constantly.
What They Actually Found
Heavy multitaskers performed worse, not better, at filtering out irrelevant information, worse at organizing information in working memory, and worse at switching cleanly between tasks. The group that multitasks the most turned out to be the least effective at the specific mental skills multitasking supposedly builds.
Why This Happens
The leading explanation is that heavy multitaskers develop a habit of treating all incoming information as potentially relevant, which is useful for briefly scanning many streams at once, but actively works against the ability to focus down and ignore distraction when a task actually requires sustained attention. The skill that gets practiced isn't focus, it's broad, shallow attention, and those pull in opposite directions.
What This Means Day to Day
"I do my best work with six tabs open and my phone buzzing" is a common belief, and it's largely not supported by what this research shows. Single-tasking with real breaks in between, the specific break pattern covered here, consistently outperforms constant task-switching for anything that actually requires sustained thought. See also 8 ways to improve focus and concentration for practical ways to reduce the switching itself.
The Bottom Line
Multitasking doesn't train focus, it trains distraction tolerance, and those aren't the same skill. If deep work is the actual goal, the research points firmly toward doing one thing at a time.
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Written by Ben Vinton
Founder, Iso-Alpha | Brain Health Researcher and Nutraceutical Entrepreneur
Ben Vinton is the founder of Iso-Alpha, a clinically studied brain health supplement built around the gut-brain axis. After watching his grandmother's cognitive decline from Alzheimer's, Ben spent years researching natural, preventive approaches to brain health before developing Iso-Alpha's patented bioavailable formula. He works closely with formulation scientists and practitioners to bring clinical-grade nutraceutical research to everyday consumers.