Eli5: Why can’t we truly multitask? Why is our “multitasking” just setting something aside real quick to do something else? Why can’t our limbs perform different tasks at once?

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Eli5: Why can’t we truly multitask? Why is our “multitasking” just setting something aside real quick to do something else? Why can’t our limbs perform different tasks at once?

In: Biology
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Basically, our brains can only pay active conscious attention to one thing at a time, called our “locus of attention”. As far as we can tell, this is an architectural limit of our brains. It’s like asking why we can’t play three-handed piano pieces by ourselves…we only have two hands. Multitasking in the sense you mean requires more than one locus of attention and we’ve only got one. As a result, the only way we can approximate multitasking is to task-switch quickly…which is actually terribly inefficient and a bad way to work but sometimes we don’t have a choice.

We can have our limbs do different things at once, but only one of them can be something requiring conscious attention. That is, for example, how we can steer our car while sipping coffee or march while playing an instrument. The other function(s) need to be something we’ve trained enough that we can do it autonomously.

Each area of your brain can only do one thing at a time; you simply don’t have any spare brain matter to devote to doing two or more similar tasks (which is not something like talking and walking, which are two different tasks in two different parts of the brain).

In an average person, the parts of your brain that control your limbs (one for each limb) could theoretically multitask, except they’re also busy coordinating with each other and with other parts of your brain. There are people who are split-brained, who’ve had a surgical procedure done that splits the connection between your right and left halves of your brain (usually done to stop seizures). In those cases, they sort of can multitask, with each side of their body able to act independently of the other. However, it’s more like they’re two individual people sharing a body rather than one person able to do two things, as their limbs can now start disagreeing with each other.

There are other good answers about the mechanics, but some evolutionary perspective is needed to explain the larger “why”. There are two good reasons. One is that multitasking, as we think of it, is possible thanks to the technology we have that has only existed a few decades or centuries, depending on what tech you mean. Our ancestors could not have multitasked with a computer, phone, car, or even a pencil.. not even if they wanted to.

Number two: it’s not a bug, it’s a feature. The distinctly human part of us that does “attention” to one thing has some pretty amazing capabilities. We can do reasoning and analysis. We can entertain counterfactuals (imagination of “what if..”‘s). We can solve puzzles, investigate questions, and in the process integrate information learned from others, from our senses, from our own imaginations, or from our previous experiences. While some animals can produce novel solutions and make tools (corvids, cappuchins, apes), no animal comes anywhere near to the cognitive prowess a human possesses to process and solve a totally novel problem or question.

But it’s not free. It involves the coordinated, integrated effort of many cognitive functions all at once. In a sense, we are multitasking. Consider, for example, someone comes to a gate they must open that they’ve never seen before. Perhaps one of those side gates at a friend’s house. Usually, a person will look at the gate and mechanism, jiggle and move bits and open it without issue in a few seconds.. even if they’ve never seen the design before. This seems very simple, but consider all the things that have happened in those seconds: the visual scene must be accurately perceived, objects recognized. Knowledge from memory is accessed to provide crucial contextual information: this device is an entry point that can be opened and closed. If a latch of some sort is visible, the person quickly reasons in their imagination space about how a bolt must be manipulated to permit motion of the door. If a latch is not visible, they reason such a device must be present perhaps on the other side and further consider its likely location. Whatever the case, they attempt to physically manipulate the latch while simultaneously monitoring the door for free movement. I’ve listed these things in a sequence, but really most or all of them would be happening simultaneously, dynamically. It’s pretty amazing really.

Our multitasking is what you call **concurrency**, which is rapidly switching between tasks to give the idea that things are happening at the same time. For example, let’s say you’re chopping onions, but also need to stir the pot every two minutes, and check in on the oven every five minutes. You can just switch between tasks every once in a while and get have them all finish at the same time–you’re not stuck doing one task at a time. The limitation with concurrency is that you can’t do two tasks at the exact same time. You can’t stir a pot while chopping onions while checking on the oven.

What you call true multitasking is **parallelism**. It’s like if in an industrial kitchen, one person monitors all the bread in the ovens, one person runs the machine for chopping the onions, another for blending the soup, etc. Unlike with task switching (concurrency), there are separate people for each task and it’ll achieve the same effect as the above mentioned with the biggest advantage being you’re doing all tasks at the exact same time. But as you can see, this is a huge waste of resources in any context than a modern/industrial one. It’d be a huge waste of energy to power an extra brain or half a brain just to do exactly what concurrency can. Plus, you can switch between tasks fast enough right now that having a parallel brain wouldn’t speed it up by that much. So from an evolutionary perspective, it doesn’t make sense for evolution to select for true parallelism when it takes a *lot* of energy to power more brain cells with minor gains in most tasks. Also remember that today we’re thinking and being stimulated intellectually all of the time whereas even 50 or 100 years ago, you’d be spending most of the day using very little processing power.

Also, our limbs *can* perform different tasks at the same time. Typing is an example, where we can coordinate 9 fingers separately all at the same time. It’s also interesting because hunt-and-peck typers put in more mental effort into typing and are slower/more error-prone than touch typists who can do it by instinct. The reasoning for that is that different parts of the brain are activated for the former and the latter. For touch typists, they skip the executive (decision-making) part of the brain completely which is why they can process the letters they need to type so accurately and quickly. This is still not true parallelism, just concurrency in that the brain processes the letters and their relative locations very very quickly so that it looks like all fingers are operating separately. It’s just due to lots of practice that this is possible, it’s not impossible for someone to learn to copy text down with both their left and right hand at the same time, just difficult and not worth the effort.

We can multitask. We multitask all of the time, even while we are asleep. We breathe, our heart beats. While awake you can do that while dancing, singing, hearing, seeing, smelling, touching and tasting.

But we have limited processing ability in our conscious minds. Our conscious minds can only do one thing at a time. That is what makes it our conscious mind. The thing we are conscious of.

You can listen to someone, do math, and process all sorts of things at the same time. You just are not consciously aware of it. When you cannot think of something, continue talking, and suddenly you remember that thing – you were multitasking. You were talking and trying to remember the thing. You were only conscious of the talking.

>Why can’t we truly multitask? Why is our “multitasking” just setting something aside real quick to do something else? Why can’t our limbs perform different tasks at once?

Your question is based on a false premise. We CAN truly multitask and we do it all the time. We drive and listen to the radio, we walk and chew gum, we stand and read signs. We could not navigate life if we could not truly multi-task.

We ARE multitasking every second. Our entire body carries out countless complex functions without even our awareness. What goes on inside our body is involuntary but that still counts as multitasking; the thing is, your body allows it do be done out of necessity. Everything from breathing, digestion to cells repairing themselves is essential to stay alive, so your body does that without you having to put in any special effort to do it and without any attention. If you could master a certain level of awareness and increase your focus, etc. it is possible to perform several tasks voluntarily and at the same time. Every thing you do requires effort and anything that requires effort can be considered a “task”. The only difference here is that we are not aware of the complex functions our body is carrying out without our awareness. Yoga and meditation is a great place to start as it can increase your focus. Our mind and body are capable of more than we can imagine!

If your brain is a computer then its software is about as bad as it could possibly be and still barely function for the needs of a caveman 200,000 years ago.