What needs to be changed in the structure of the human brain in order to give it better multitasking?

Question

The brain of a modern person can execute dozens of thought processes without overflowing. And parallel multitasking has a clear survival advantage.

How do you need to change the human brain (if necessary, you can radically alter it) so that it can cope with several (more than four) separate tasks at the same time? For example, this genetically modified person could easily view four separate streams of data on four different subjects (for example, watch four different films or read the same number of different books or magazines) at the same time and receive complete information from all of them. Or that it would also be nice to watch one tape of data, listen to another, simultaneously have a more or less full-fledged conversation with a person or a group of people and at the same time write something with two different hands.

Answer 1

You don't need to add to it. You need to remove from it.

The human cerebral cortex really behaves like two brains, the left hemisphere and the right. Between them is the corpus callosum, a thick bundle of fibers that connects them, letting them talk in a very rapid fire way.

In the last seventy or so years, doctors have done corpus callostomy operations, in which they sever this connection. It is typically done on patients suffering from severe epilepsy for which less invasive treatments simply aren't working.

The result is a patient whose epilepsy goes away, but otherwise seems normal. At least, they seem normal until you start probing at the corners of how they behave. If you start doing things like putting objects in the left eye's field of view, which is handled by the right hemisphere of the brain, and then asking them questions about it, the effect of this brain surgery becomes apparent. The effect is known as split-brain and the results can be uncanny:

The first test started with a board that had a horizontal row of lights. The subject was told to sit in front of the board and stare at a point in the middle of the lights, then the bulbs would flash across both the right and left visual fields. When the patients were asked to describe afterward what they saw, they said that only the lights on the right side of the board had lit up. Next, when Sperry and Gazzaniga flashed the lights on the right side of the board on the subjects left side of their visual field, they claimed not to have seen any lights at all. When the experimenters conducted the test again, they asked the subjects to point to the lights that lit up. Although subjects had only reported seeing the lights flash on the right, they actually pointed to all the lights in both visual fields.

or

... a patient with split brain is shown a picture of a chicken foot and a snowy field in separate visual fields and asked to choose from a list of words the best association with the pictures. The patient would choose a chicken to associate with the chicken foot and a shovel to associate with the snow; however, when asked to reason why the patient chose the shovel, the response would relate to the chicken (e.g. "the shovel is for cleaning out the chicken coop").

This also leads to the famous alien hand syndrome seen in Dr. Strangelove, where a hand has a mind of its own:

The callosal variant includes advanced willed motor acts by the non-dominant hand, where patients frequently exhibit "intermanual conflict" in which one hand acts at cross-purposes with the other "good hand".[15] For example, one patient was observed putting a cigarette into her mouth with her intact, "controlled" hand (her right, dominant hand), following which her alien, non-dominant, left hand came up to grasp the cigarette, pull the cigarette out of her mouth, and toss it away before it could be lit by the controlled, dominant, right hand. The patient then surmised that "I guess 'he' doesn't want me to smoke that cigarette."

Answer 2

Simply larger

I feel like you're mostly thinking about the conscious mind. However, the mind has a much stronger subconscious part. This is well evident in how it processes things. Every day your subconscious is filtering through your daily life, ordering all visual, tactile, proprioceptive, taste, hearing and smelling stimuli. This creates both a conscious and subconscious view of the world. It pushes some things to the conscious, like your name over the din of a crowd, or a familiar face, or a hamburger joint while you’re very hungry. Subconsciously you’re still processing a lot more, from idea’s like what to write to that mean poster on the internet three days ago, to what car you should buy, or simply driving you home in the car while your attention was completely somewhere else.

Consciousness can in a very crude way be seen as a filter on the subconscious. Anything deemed important enough is pushed to the consciousness, which will allow it to be more easily stored in memory and reacted to more actively.

The question then is, why can’t we already multitask incredibly well? First of all, as the most intelligent species of the planet, we can. Just not as well as you would like as an answer. The part of the brain that gives us our intelligence is relatively young evolutionary speaking, which is very visible if compared to the limbic system, cerebellum and brain stem. The density of these older systems of the brain is much higher and has more surface area thanks to sulci and gyri (what makes the brain look like a wrung out sponge). Our current intelligence is simply fledgeling and only just capable of sustaining the amazing things we can do currently. It can even be seen in the ‘leaking’ of information from one part of the brain to the other, where stimuli of for example a body part can leak into the neighbouring brain area, causing you to feel some things there as well.

How would we improve? Simply by making it more densely packed and larger, with more sulci and gyri. This way, we’ll be able to process much more information with less leaking, as long as the nutritional supply is enough and further strain to each brain volume isn’t increased. Otherwise many stress symptoms can be seen quite quickly, or simply shut down or death from malnutrition. Increasing your brain volume will also increase brain power, allowing to process more, deeper and faster on both a conscious and unconscious level.

However, we have a second barrier we already deal with every day. Not only is the brain holding us back, our physical body does so as well. Our eyes have only a small focal area, meaning you simply can’t see four screens effectively at once. Even rapid switching from screen to screen will make you drop a lot of information in the saccade (quick movements) of the eyes. Our smell and hearing are very limited compared to a lot of other species. Our hands do have an insane amount of tactile sensors, but most of our body doesn’t. Many parts even share sensory input, like the back that has many tactile sensors that are registered on the same neuron to the brain. This obfuscates many information, which is fine for our lives but maybe not so much for your super humans. If the brain capacity has been increased, more stimuli can be processed as well.

In short, our brain is already impressive, yet fledgling. Making it larger and more developed in density and surface area will help a great deal. In addition, improve the body to increase the capable stimuli density. Otherwise you’ll never be able to have the required input for your desired multi tasking.

As one addendum, I think no ‘second’ conscious is possible. However it’s damn hard to imagine with only one consciousness, so how can we know? For all we know our subconscious is much like our normal consciousness, just It’s very good at keeping temperature, heartbeat, breathing and the odd movement of an arm or so.