Well, I can say from my personal experience that multi-tasking up to some level and within a distinctive box benefits you to grow and learn new things. In other words, it can be called as "slow-motion Multitasking".

I personally force myself to learn and try out multiple things in a day and when you can cluster them into multiple boxes and proceed, it proves out to be useful enough.

Multitasking is popular because it gives the impression of being more productive (or at least busier!)

But science tells us it’s not true. The attention span of an average human is usually in the 5 to 7 chunks. And then there’s all the context. The more you multi task, the more context you have to re-load.

One efficient way of doing kind-of multi-tasking, is to use all the parts of your brain efficiently: you focus on a problem/task for some time, and when you’re stuck, then you switch to something else (again, for a minimum amount of time). Your conscious focus will switch from one task to another, but your brain will keep thinking about the other task, so that when you come back to it, you might make quick progress.

That’s part of the mechanics at work when people use the Pomodoro technique.

If you are not familiar with how your brain thinks and how the conscious vs unconscious thinking process work in parallel, a great introduction is this talk by Linda Rising:

When people are "successful" multi tasking, usually it’s because only one task really requires a full focus, and the other(s) one(s) can be automated and does not require any active thinking. Otherwise, the focus and the cognitive load is split and indeed, either the tasks are really simple, or they aren’t performed as well as they could.

As soon as a task requires some focus and concentration, your brain needs to be fully engaged.

The sooner a developer learns this, the sooner he improves on complex tasks.

Thankfully many tasks are dull and don’t require a full attention ;)

Back when I was in school, I am a multitasking monster. I play games while eating and talking, I work on assignments while watching Netflix (I don't know how I did that) and my favourite multitasking activity:

Reading while listening to music, talking with my friends and eating all the same time.

But then I took a course on psychology and my professor told me that multitasking is not efficient and results are often less productive. In terms of cognitive functions, it reduces social awareness and memory retention since your brain can only focus on one thing at a time. In short, multitasking leads to breadth instead of depth activities. Since then, I started to reduce multitasking.

I found that I can focus for longer periods, work on assignments more efficiently and pay more attention to detail in my work and surroundings. The highest level of multitasking I do now is probably just listening to music while working. In conclusion, I'd say yes multitasking is evil, especially for software engineers who often has to focus and work efficiently for a long time.

I can't speak for everyone, but for me it is evil. A necessary evil, though. I wish I lived in a world where I can give this one task my undivided attention, complete it fast enough and move on to the next one, but that's not the case.

As a Software Engineer, even multitasking on a very small scale troubles me, but I end up working on that code while replying to my slack messages and checking open tickets that has been assigned to me or reading that article about this new framework, as I attend that Zoom meeting and fill out the registration form to attend this upcoming talk. I believe it slows me down and exhausts me, but I have to keep up. Sadly, time is not always on our side. You not only have to keep your deadlines in my mind, but others, as well. There is always that urgent reply that is needed and that application closing date you don't want to pass and that launch you don't want to mess up. We are always running from a monster we can't see and I don't think any amount of time would ever be enough.

Even in my personal life, I would be leaving the chicken cooking on the stove, while I am checking on my grandma on the phone, as I fold the laundry, because no matter what, I only have 24 hours. It's inevitable!

Project management tools are really of great help to me, though, on both the professional and the personal level. Every week, I sit and write everything down. I start planning what I need to do and prioritize what absolutely needs to be done and what can be pushed for a later time, in case something came up and just go from there crossing my fingers and hoping for the best.

Human Multitasking to me, only works if the tasks are not complex and don't need complex analysis but mainly execution.

I can fold my laundry and talk basically. I can write a simple HTML form and switch between an email and talking to a colleague. These are things that I trained a lot there is no learning involved just acting on a subconscious level.

Any multitasking within a creative process that is not already broken down to smaller pieces that have well defined boundaries seams counterproductive to me.

that's my experience.

To be honest, I am very bad at multitasking. I always end up switching the tasks. Complete one peacefully, do the justice to the work and then move on.

I think most of the time, people would expect you to finish n number of tasks within a certain time period. The best thing to do in such cases would be to divide your time by n and then proceed.

This would give you an idea whether it’s possible to finish all the n tasks in x time.