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
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.
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