The way I see it is that we are born with an inherent disposition towards a certain attitude.
Some people are born really kind, but their experiences will either enhance it, or dull that personality trait. For instance. Mahatma Ghandi. Everyone knows who he is. He was known for liberating India. But what most people don't know is that he was regularly beaten and punished for being Indian. Now, he had two options here. He COULD have turned against them and strike them(like most of you would have done) but no, he followed his inate personality. He rose above the prejudice, and become on of the worlds greatest protestors of violence.
Some people are born more intune with their animalistic side. Again, life experiences either enhance, or dull it. I have this aquaintence, shall be named Bob, that was a bully from the moment he could crawl. Slapping his younger and older sisters, stealing their food, what ever he could do, he did it. He ended up growing up to be a complete dbag. Everyone hated him for his attitude. He only got worse and worse. Now, my sister met this guy when she was six or so. She tried being friends with him. Failed. We moved to another city, and they didn't see each other for about 20 years. They reunited while he was in prison(for armed robbery), and she was working there as a parole officer. She took a special interest in him(ended up getting married), and it literally changed him. He's now one of my best most reliable friends with a promising future in MMA. He has won several world championships in the last 5 years. 3 Golds, 2 Silvers.
You can't fight your inherent disposition, but you can certainly change the degree that it effects you.
As for the multitasking thing, we can't just split our attention into two pieces. Our brains don't work that way.
We can focus on one thing with one half of our brain, and another. Through this, and practice/development of our brain, we can multitask with our bodies. Ever tried rubbing your stomach, while patting your head? Then switching? Well, it's difficult/almost impossible to do at first, but over time you can train your body to do it. However, your two halfs of your brain are working as one at that point. Originally, they were working together, clumsily. (right brain works the left side of the body, and left side controls the right) And after training, your two halfs start to work together more efficiently. They cannot, and will not work seperately. Brains, 99% of the time, can't do seperate things. They may seem like it, but studies have shown that your brain "translates" the seperate processes into a series of single commands that your body then performs.
and focus our cerebrum on another(the part that handles our coherent thoughts). We can control our bodily functions with the medulla oblongata, and we can do two simultaneous things with our body(or more) with practice, but we can't think two different simultaneous trains of thought.
Your cerebrum can't focus on two different things at once. It thinks of itself as one. It may have hands and feet(metaphorically) that it can grasp onto seperate things, but it becomes cluttered and confused. Try calculating how many seconds are in a day, while reciting the national anthem from memory. It's not possible to do, without practice. But when you do manage to be able to do it, through practice, your brain doesn't see it as two different processes, but a single integrated thought process.