May 06, 2015
It's a curious fact that in medieval times people had more leisure; they had lots of Holy days (holidays) and took breaks and siestas during the day. Contrast this with modern man who thinks he's gaining by working while eating his lunch. His work and health suffers and he loses sight of the wider picture. He spends a lot of time on something that might not need to be done at all or could, with some perspective, be done differently.
In the 1980's the golden years of the boom in financial services industry began. "Multitasking", derived from computing terminology, became something for humans be proud of. Men had breakfast meetings at 7am while getting a massage. Women juggled baby, phone and liaising with the office. Being busy was taken for being successful. High-fliers wore braces and burnt out early. Illegal stimulants made you feel like a million dollars while you negotiated million dollar deals.
With the advent of email, websites and even smaller mobile phones, a man could run an empire, from a loft in San Francisco, while his wife worked for a realtor and the children were hothoused in pre-school.
There only one problem with doing 3 things a once: we can only concentrate on one task as a time. The others will suffer. Unless ...
... they are robotic tasks our lower brain can take care of quite happily.
Even then, would you bet on a batsman who was chatting on his earpiece while playing at Lords?
Answer: yes, depending on who he was talking to and what about.Why?
Well, that part of his brain which would normally be fretting about hitting the ball, but which plays no part in actually striking it, would be engaged in talking with his wife. So he would hit the ball more cleanly. This would not work if he was talking with his accountant; that could be serious business! Anything banal that usefully occupies the forebrain (chatting with mother) while the cerebellum takes care of the physical action, can work well. 
What does not work is trying to do 2 or more intellectual tasks simultaneously e.g. read a book and have a serious conversation. What the mind does is switch from one to the other. You may think you're doing both well but anyone who's tried to chat to the girlfriend while watching TV knows that both conversation and entertainment suffer! What the brain is doing is switching from one to the other; you're not actually doing both at the same time. Unlike a computer, you do not have 2 or more CPUs!
Multitasking in the corporate environment means doing more work for the same money and giving 'face time'; you must be seen to be working hard. You may also have to work hard to keep your place; the owners of blue-chip corporations take a mathematical view of labour! It's also a peculiar badge of distinction.
This is of no use to the entrepreneur; he wants tangible success, not just the appearance of it.
So you can do 3 tasks over 5 hours, as long as you avoid doing 2 physical or 2 intellectual ones simultaneously!