is multitasking is a myth?

[BrittleQuarry]

Going to say something that tends to annoy people, multitasking as most people describe it barely exists, what's actually happening is rapid task switching with a real cognitive cost each time you switch. Research on this has been fairly consistent for years now, showing measurable performance drops when people try to juggle multiple demanding tasks simultaneously rather than sequentially. People who genuinely believe they're great multitaskers usually test the worst on actual task switching studies. Feel free to try and change my mind here though

The usual pushback is that some tasks are genuinely low demand enough to run alongside something else without real cost, like listening to music while cleaning, which I'll actually grant as a fair exception. The real disagreement is usually about actively demanding cognitive tasks specifically, like writing an email while also on a work call. Curious if anyone's actually got solid evidence against the core claim rather than just a strong personal feeling about it

So change my mind if you can. Genuinely open to being wrong here if the argument's actually good