As much as we humans like to think we can do two things at once, our brains can only process one thing at a time—like the iPhone—but we can get better at switching between the two tasks, according to a study published in Neuron.
Previous studies showed that multitasking activates the brain’s prefrontal cortex, or PFC. This area has been found to be the “bottleneck” that can limit the speed at which we multitask, and it becomes less active as we practice doing two things at once. The prevailing theory for that decreased activity had been that when we practise a task, the brain starts to automatically reroute information from the PFC to regions that are more directly involved [Nature News].
To investigate, researchers used fMRI scans to monitor brain activity by tracking blood flow while subjects multitasked, and found evidence that the previous theory was incorrect. The scientists found that a junction in the PFC which passes signals to other brain regions responsible for performing each task responded earlier and for a shorter duration than before [in volunteers who had practiced multitasking], indicating it was processing information more quickly. “This suggests our brain becomes better at the task with training, not by reducing the dependence on [the PFC] but rather by improving the processing efficiency [of each task] through this bottleneck,” says Marois, who acknowledges that other regions are also likely to be involved [Nature News].
The study also contradicted another theory of how we become more efficient multitaskers. That theory predicted that with practice, the brain learns to designate separate clumps of neurons, or brain cells, to perform the different tasks, instead of relying on the same cells to process information for both of them. This study, however, found no evidence of distinct groups of neurons operating in parallel, and instead showed that the same neurons are simply operating faster. So we’re switching tasks quickly enough to appear to be doing them simultaneously [Scientific American].
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Image: flickr / Liz Henry
July 20th, 2009 at 11:18 am
I wonder how this matches up with the idea of our zombie brain (an earlier mind post on these blogs).
July 20th, 2009 at 6:39 pm
I thought males, who are mostly left-brained, could multitask, and
females, who are mostly right-brained, could not, generally speaking
July 21st, 2009 at 1:07 am
You don’t think women can multitask?? Have you ever met one?
July 21st, 2009 at 1:35 am
That whole left/right brain dichotomy thing is a myth, stemming from research on stroke patients back in the 50s. The brain is much more complex than that.
And that whole difference in brains between the sexes comes from sexist culture.
July 27th, 2009 at 4:32 pm
I took a course in this and was told that people with a good connection between the right and left lobe were good multitaskers and that woment usually had the connection and men rarely did. I was all excited because the test showed I had the connection too – they assured me it didn’t mean I was gay. It seemed like a good theory as each half processes different kinds of information.
July 27th, 2009 at 5:06 pm
This makes me wonder if any of these results also correlate with being ambidextrous?
July 27th, 2009 at 6:25 pm
I wonder if there’s something else involved in activities that get fully automated . . .
I’m thinking about such things as driving or playing a particular song on the piano — that perhaps the brain does still push some functions down to areas of the brain or central nervous system (or that those parts of the brain/CNS become efficient enough to not need much involvement by the cortex). When I first learned to drive, it took everything I had to make sure I was getting it all right: scanning where I’m going and the traffic situation, shifting, traffic rules, etc. Now, the physical act of driving seems automatic and I can talk on the phone (hands-free, of course :) ) and only need to focus on driving when traffic gets interesting. Likewise, when I’m learning a new song on the piano, it’s the only thing I can do. One that I’ve been playing for years I can play while chatting, thinking about other things, etc.
What about something even more fundamental like walking. I’m sure a baby is burning up the upper level neurons to balance and put one foot in front of the other. I like to think the walking is pretty automatic (autonomic?) as I chew gum and maintain a conversation while walking.
July 29th, 2009 at 12:41 pm
Sometimes when I’m driving, and immersed in conversation with one of my kids, I’ll accidentally pass my intended offramp because I’m mindlessly headed towards work.
August 25th, 2009 at 8:14 pm
Small nitpick, but there’s poor terminology in the article. It starts with the title, “Key Brain Section Never Multitasks—It Just Switches Very Fast”. This implies that the choices for the brain are (or were) multitasking versus task switching. That’s an over-simplification.
We see this in information technology, where these issues have been worked on for many years now. The traditional distinctions, in increasing order of technical complexity (and corresponding user capability) are: single tasking, task switching, multitasking, and parallel processing.
In single tasking, only one thing is being done. In order to do another, the first task must be “put away”, likely to it’s permanent home (storage). This is almost always a manual step too.
In task switching, only the forground task gets any processor time. Background tasks exist (versus single tasking, where there’s no such thing), but a background task is completely inert. The background is a temporary place to put a task, from which it can more quickly be revived by bringing it to the foreground. Again, in every case I can think of, this is a manual step.
In multitasking, both foreground and background tasks get processor time and are therefore “active”. Scheduling algorithms typically chose to give the foreground task more time than background tasks, but both can accomplish work. However, and this is important, there’s no need for true simultaneous activity. Multitasking computers have been around a long time and have no absolute need for parallel work. The computer accomplishes this bit of magic by extremely rapid, entirely automated task switching. The appearance of several things happening simultaneously is just that–appearance. Human perceptual limits mean that we cannot perceive that everything is in fact happening serially (I’m deliberately ignoring I/O buffering, which does allow a very limited amount of concurrent activity).
Then you get to parallel tasking. In this architecture the compute system actually has multiple processing resources and can truly do 2 things at exactly the same time. The latest CPU’s from Intel and AMD have multiple cores that not only provide this capability, but do so at an extremely reasonable price, cheap enough for the majority of PC-type computers to come with this as standard equipment.
The brain is an interesting case. My understanding is that at the micro level, it is massively parallel, and there’s no way (not that you’d want to) turn that off. However at the macro level, the level of consciousness and awareness, it’s single tasking (oops, task switching).
This leads to the phenomenon of people being less safe while driving and talking on the cell phone–it takes a person a finite amount of time to switch tasks. Their attention can be on the driving or the cell conversation but not both simultaneously. Faster switch times certainly help but do not entirely resolve the competition for the person’s attention.