Its a proven scientific fact that the Brain does not really multi-task, it switches from one task to another, some people are real good at the switch and some are not. It is my opinion that focusing on completing one task at a time is the best way to successfully complete task. I say that as I sit here multi-tasking so there you go.  :) 

I have been in customer service for the past 40 yrs. I have always multitasked. With working on the phone with people , you do have to multitask. I think that multi tasking is a necessary part of work and home.

You know, you hit the nail on the head.  I was pondering this very question the other day.  I am a drummer.  I multi task just to play.  However, muscle memory is what helps a drummer.  Meaning. my arms and legs do their thing without me thinking about them.  So, left leg, right leg, right arm, left arm all work together but, independently.  Now, when I sing, I cannot think about legs and arms, only words and pitch.  So, am I really multi tasking or just thinking about each item for a split second and moving along?  Do I want my dentist drilling on my teeth and shining his shoes at the time time?  Or my carpenter to cook lunch while he saws my lumber?  Hmmm?  Multi task?

Some people don’t like crowds or big cities or lots of noise or being asked to do multi tasks.. others thrive on it. As a former (and too often needing to be) an emergency room veterinarian I need to multitask. Contrary to a comment I just read (which prompted me to write this) no one’s s brain is or isn’t able to process multiple tasks! Some people just do it and thrive, others do it and burn out, others just don’t want need or likely not be able to do well with it! Conductors at a symphony is an easy example. They have to make a lot of different people sound great together.. like a choreographer or a swat commander… lots of info need to make it work and do it correctly. A teacher with 25 kids! Omg. I LOVE multitasking. I sit with a grieving client, hug a new puppy greet an old furry friend, calm an anxious cat and owner field phone calls emails and decide if that is a dog gagging on a toy his owner refuses to believe he ate or treat that pet in heart failure. Oh my… the art and fun and thrill of saving a life or being there to comfort one that needs to be let go peacefully. I’m in awe of successful multitaskers and patient with those that can’t. What I hate is a non multitasker doing an awful job and being frustrated. Or a lazy person who could do so much more but picks the easy way . I just think we are all different and the ones that don’t burn out or do a bad job are the blessed that found something they love and thrive in learning more about what ever is presented to them in their niche! 

Excel at a task, or complete multiple tasks at once? There's a difference. Ask any young mother and I will guarantee you she tells you multi-tasking is possible, and necessary for survival. Women can be on the phone making an appointment with a doctor, while feeding a baby and playing tic-tac-toe with a toddler. 

I believe that multi-tasking is a great quality for a person to have, some people just can't do it, however I have been doing it for years and not only does it keep you busy it also makes the time go by quicker. Yes, there are people who can only focus on one thing at a time so if you need several things done then you are going to need that person that can multi-task and do it very well. I also think that several jobs now a days need you to do more than one thing at a time and it opens up more opportunity for someone if they can do it. I do it at work every day as well as at home, when I do it at work sometimes, I am doing 3 to 5 things at a time, but I am used to it.

My simple answer to a complicated question is that I need to multitask to get everything done in a day and not get behind. Sure, things are not the same quality initially but it is a skill that can be honed if your brain is wired to do it. Some people cannot and should not attempt it. Everyone's brain is wired differently. If you are not successful, don't do it, lol!!! 

The human brain does not multi-task, it switches rapidly between tasks, with a time loss while switching.  The context switching time is lost forever. To be more efficient, people should perform one task until they reach a logical stopping point - need more information, a step fully completed, etc. While it makes sense for a production line to all take their break at the same time, people performing solo tasks should take their coffee breaks based on reaching a logical stopping point and not based on the clock.

There's no such thing IMHO.  There are only some who can shift their attention much faster than others (professional A.D.D.).  "multi-tasking" was a vogue term introduced by executives in project management back in the 80's when the name of the game was to squeeze as much as you could out of your people to save a buck.  for most people in the real world, its the fast track to burn out.  Excellence requires focus.

It all comes down to Time management, You can be just as focused doing 3 things as One, I am sorry, if you are proficient at what you do, while on hold, you can text, search your lap top, continue on your call and list what you need to do next. i would hate when my Assistant would stare into space while on hold. Line up your next task, list the priorities of the rest of the Day, look up and delegate a task, how can you function Today and not mange multiple tasks? If you are just doing one thing at a time, save accounting and the like then you are losing valuable time. I am over 55 and have been this way since my Teens, I have become adept at it and I am not slowing down I am taking on more. It's how I roll and it works. I revel at what I can get done in a day and yes, it depends on the tasks naturally. That's not to say I may pause to answer a question or stop typing to continue a conversation in person but how many people talk, write and use their computer at the same time? That is Multi tasking!