If I remember from my degree, its a quality of depth/focus issue. Your brain settles into a task and unpacks that task (with all kinds of consideration for mental load, familiarity, etc). This takes about 20 minutes to get properly focused.
Switching the context pops you out of that task, and then your brain has to resettle into the new one. You don’t get a bonus for switching between only two tasks, it takes about 20 minutes each time.
So multitasking is effectively ruining your own focus everytime you switch, which is why they’re slower - you restart the 20 min clock every time you switch. Ppl doing familiar tasks can switch a little faster, and sometimes there’s a level of quasi-multitasking where you can work on automatic - but it has to be below conscious processing to happen (e.g., driving and then not realising how you got where you’re going, or you’re already intimately familiar with a file at work). It doesn’t quite count because your conscious processing doesn’t come into play, so it’s not really switching






Depends on the person, I think. I hate my phone, and keep it as a requirement to stay connected in a modern world.
The knock-on effect of that is that I’m constantly overdrawn, and have little energy for the ppl who reach out to me, nvm the ppl I’m now supposed to reach out to.
Just my experience but I don’t think totally invalid