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The term ‘multitasking’ originates in a 1965 paper published by IBM.
This paper described the computational heft of a new mainframe product called the IBM System/360, which at its most premium specifications was augmented with multiple selector channels which could operate in parallel. This improved its overall performance by allowing it to perform multiple tasks simultaneously.
That same decade, psychologists began investigating multitasking in human beings.
Initial research focused on what became known as the psychological refractory period, or PRP.
The PRP refers to the time it takes for a human brain to switch between two tasks, that time measured in terms of what’s called stimulus onset asynchrony—which means, essentially, how long it takes a person to shift from processing one input to processing a second input that is presented in rapid succession.
Early determinations found that while there are quite a few discernible variables that influence a person’s PRP, some elements that were theorized to impact our ability to quickly switch our focus from one thing to another do not seem to play a role.
A person’s personality, for instance, doesn’t seem to tell us anything about their abilities in this regard, nor does their place on the introversion/extroversion spectrum or their measurable intelligence level.
Interestingly, both alcohol and caffeine can negatively impact an imbiber’s performance on PRP tasks. Alcohol has been shown to decrease performance in both speed and accuracy, while caffeine can increase speed at certain doses while reducing accuracy across the board.
The most prominent and widespread variable in PRP performance, though, seems to be age. This is thought to be the case, in part, because of how our cognitive processing mechanisms seem to function; one common metaphor used to describe this functionality is that of a bottleneck.
If you picture neurons shuttling around in our brains, taking information from one place to another anytime we need to process something that’s happening, you can imagine how a those neurons might respond when one type of input is interrupted by another: they’re still in-transit, and it takes a moment (measured in brain-time, so it’s quite fast in human-scale time) for them to arrive at their destination, get the new information that’s just arrived, and shuttle off to their next destination with that data.
This is the lag we see when a person attempts to process multiple stimuli, and the bottleneck arises for the same reason a lot of cars on the road can slow down traffic: there are only so many channels that can be traversed, and only so many cars available to move information from one part of the brain to another.
Extending on the lack-of-cars component of the bottleneck metaphor, the economy of the human-processing system says, in essence, that our finite number of mind-cars may also play a role here, because even if the traffic is light and no bottlenecks occur, we still only have a finite number of information-shuttles available. Thus, no amount of parallel processing capabilities will give us infinite processing abilities: we just don’t have the cognitive capacity.
When viewed through the lens of attention—which is our ability to choose to focus our cognitive resources on a discrete piece of information or stimuli—multitasking is an attempt to divide our attention between two or more things rather than dedicating it all to just one thing.
Although there have long been theories about how we might be able to listen to an audiobook while reading a blog and watching a sunset, because maybe these different sorts of sensory inputs use different parts of the brain, modern research indicates that this is almost certainly not the case.
Studies measuring the effectiveness of drivers who talked on the phone while performing different driving-related tasks, for instance, consistently showed that performance of both driving and speaking decreased. And although there is some evidence that a person might be able to train themselves to perform some types of repetitive tasks alongside other, more cognitively demanding tasks, with largely undiminished capacity, most tasks that involve novel stimuli or some level of non-repetitive, non-reflexive thinking seem to be performed less-effectively and slower when combined.
Multitasking, then, or continuous partial attention, as it’s called in its chronic form, is generally unadvisable, as it can render us less cognitively capable according to multiple metrics—which in some cases will lead to more mistakes, in others will result in slower-than-average processing, and in other cases might result in sloppy driving, walking, or thinking.
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