Research Suggests Brain Has a 2-Task Limit for Multitasking

suraj.sun writes with a story from LiveScience about just how much attention you can devote to each of the tasks on hand that scream for it: "The brain is set up to manage two tasks, but not more, a new study suggests. That's because, when faced with two tasks, a part of the brain known as the medial prefrontal cortex (MFC) divides so that half of the region focuses on one task and the other half on the other task. This division of labor allows a person to keep track of two tasks pretty readily, but if you throw in a third, things get a bit muddled. 'What really the results show is that we can readily divide tasking. We can cook, and at the same time talk on the phone, and switch back and forth between these two activities,' said study researcher Etienne Koechlin of the Université Pierre et Marie Curie in Paris, France. 'However, we cannot multitask with more than two tasks.'"

Comments

I must be the human iPad

[Dachannien]

So how come I can't walk and chew gum at the same time?

Re:I must be the human iPad

[JustOK]

I can eat popcorn and chew gum at the same time.

Re:I must be the human iPad

[Lord Lode]

An iPad can multitask more, it can do 3 tasks at once: you can put a beer glass, the bottle and some food on it at the same time!

How quickly can I get my boss to ignore this?

[cavehobbit]

7 projects, 2 of which are corporate mandates with no additional funding or 'resources' to do them, 4 other administrative tasks, plus an hour or so each day dedicated to HR-related corporate marionette-ing to satisfy the Political Correctness Police. All for 2 shell scripts and a mainframe extract. That took 3 months to get done. And this isn't even a government job.

Bullshit.

[Anonymous Coward]

I call bullshit. Right now, I'm replying to this Slashdot article from my cell phone, eating a quick breakfast, and driving my car in morning traffic. I'm doing all three with the utmost saf

what is a single task to the brain?

[slashmojo]

Is talking on the phone really a single task? Is cooking? Surely each of those is made up of countless sub-tasks even if you don't consciously think about them.

Re:what is a single task to the brain?

[Pharmboy]

Is talking on the phone really a single task? Is cooking? Surely each of those is made up of countless sub-tasks even if you don't consciously think about them.

If you were just saying random words, then perhaps not. But if you are discussing the new project at work, or what little Johnny did at school, or even about sports, it requires pulling in previous experiences, remembering specific events, drawing conclusions, etc., which are "subroutines" in a single task, communicating. A phone conversation can actually take more brain power than driving down the highway. Think about it, when someone is driving and talking on the phone, it is obvious that the cell phone requires more attention than driving. As for being sub-tasks, all tasks are generally linear subtasks that would qualify as a single task.

Perhaps that is why people tend to stray into the other lane when driving/talking on the cell. A third activity comes in or they have to fork a thought for consideration during the conversation, and they run out of brainpower/memory, so the least important activity (driving) gets swapped out for a second. Humans just need more RAM.

How about that, a computer analog for a car problem, instead of the other way around!

Re:what is a single task to the brain?

[UpnAtom]

Especially in men, right brains don't talk. So that's exclusively left-brain.

Driving (at least the direction & speed control) is right brain. The time it's most likely to engage your left brain is when you have to consciously think ie planning your route, adapting to unusual road conditions. Apart from that driving & talking is fairly easy for experienced drivers. Typically, drivers talk in a monotonous voice as inflection is right hemisphere.

Try adding a column of figures eg restaurant bill and having a conversation at the same time - pretty damn hard because both are left brain. So there we're only single-tasking.

I think what this research shows is that we use both sides of our brain when we're single-tasking. Some areas of the brain are very specialised but other areas can be trained to perform similar functions (for some people, the right hemisphere spelling a word would be an unnatural task). If we're doing two tasks for which different hemispheres of the brain can assigned one of the tasks, then the brain is quite adept at dividing up the workload.

Re:what is a single task to the brain?

[daveime]

Is talking on the phone really a single task?

According to Steve Jobs, a definitive "yes" (until version 4 is released anyway).

Re:what is a single task to the brain?

[BikeHelmet]

Humans seem to have about 4KB of RAM and one freaking huge hard drive.

Think about it - the access latency matches up! ;)

It should be noted that while we have a HyperThreading prefrontal cortex, we also have cores available doing background tasks, like managing movement, processing what we hear and see, alerting us to sudden movement/danger, etc.

Re:what is a single task to the brain?

[Theril]

I don't think that the hemisphere-function division is as straightforward as you, and much of popularized psychology, suggest. From eg. lesion studies the evidence seems to hint that there are some tendencies to somewhat specialized functionality in the hemispheres, but these are quite "vague".

Some quotes from Wikipedia to back this up:

"Broad generalizations are often made in popular psychology about certain function (eg. logic, creativity) being lateralised, that is, located in the right or left side of the brain. These ideas need to be treated carefully because the popular lateralizations are often distributed across both sides."

"Hines (1987) states that the research on brain lateralization is valid as a research program, though commercial promoters have applied it to promote subjects and products far outside the implications of the research. For example, the implications of the research have no bearing on psychological interventions such as EMDR and neurolinguistic programming (Drenth 2003:53), brain training equipment, or management training."

http://en.wikipedia.org/wiki/Lateralization_of_brain_function

Also the study that the article refers to does some quite bold assumptions about how brain works (eg. quite strict functional localization) and the whole concept of "task" is so generally defined that it's quite easy to escape any falsification by modifying its properties.

In general, most of the stuff about psychology/cognitive science that "leaks" to public should be taken with a grain of salt. Much less about brain functioning is known that may appear to a casual reader, or to some self-criticism challenged researchers.

Re:Oh no !

[jimmydevice]

Yes, you are chewing gum while listening to music and posting to Slashdot.
How is this multitasking and not slacking?

Please define task

[houghi]

I can eat, breath, type and read at the same time while listening to music.
At these moments I am also thinking ahead of what I am going to do.

Even typing could be considered doing several tasks at the same time. The sample of 'cooking' in the summery can be defined as multiple tasks. You are standing, you are tasting and smelling, you are planning of what to do next and probably stirring as well as looking.

For a chef in a kitchen, cooking is also interacting with other people at the same time.
For some people cooking is pressing the button on the microwave and waiting for the 'ting' of the machine.

So what is a 'task'?

Re:Please define task

[Skexis]

If you require constant attention to keep breathing, you have bigger problems than defining a task. But from TFA:

Koechlin and his colleagues had 32 subjects complete a letter-matching task while they had their brains scanned with functional magnetic resonance imaging (fMRI). The subjects saw uppercase letters on a screen and had to determine whether those letters were presented in the correct order to spell out a certain word. They were given money if they performed the task with no errors.
...
But then they made the task more difficult. In addition to uppercase letters, the subjects were also presented with lowercase letters, and had to switch back and forth between matching the uppercase letters to spell out, say, T-A-B-L-E-T, and lowercase letters to spell out t-a-b-l-e-t.
...
To make things even more complicated, the researchers introduced a third letter-matching task. Here, they saw the subject's accuracy drop considerably. It was as though, once each hemisphere was occupied with managing one task, there was nowhere for the third task to go.

Re:Women can do it better..

[Rogerborg]

Based on this research, it would appear that women are better at cooking and talking on the phone. Gasps of surprise, and film at 11, probably something with Renee Zellweger being charmingly quirky.

Musicians

[Landak]

What about professional musicians, who have to concentrate on far many more things than two at once? Organists, in addition to playing anything up to five keyboard manuals with their hands and one with their feet (simultaneously reading anything up to twelve lines of music, though in practice usually never more than five), have to listen to a choir and/or congregation, watch a conductor, and read the music, all at the same time. Some of them can even sing competently one line whilst doing so!

Whilst I can accept that it is very difficult to consciously concentrate on more than two things at once, somehow some people can train their subconscious into doing so -- when sight-reading music, I experience a lovely sensation, almost as if my brain is being "split" down the middle -- if I concentrate for too long, I start to develop a headache and feel exceptionally exhausted. It is a most wonderful feeling, and nothing else in the world quite comes close (although doing some rewarding mathematics isn't far behind). I would not be surprised if it were possible to find many more examples of people concentrating on more than two things at once, "simply" through getting other bits of their brain to do the dirty work. Juggling on a unicycle while jumping over a skipping rope, anyone?

Re:Musicians

[cthugha]

As I remember it, all of that repetitive fine motor control musicians need is handled by the cerebellum at an unconscious or preconscious level once the necessary movements have been learnt (this is why practice is important). So yeah, there is division by delegation of many tasks, like you said, but I'm not sure how many pure "thinking" processes could be performed at any given time.

Re:Musicians

[phantomfive]

Reading the study (actually the summary), I think the problem is the people doing the test weren't actually switching tasks, they were trying to focus on all the things at the same time. I notice that when I work on multiple things (for example, music), I am actually switching between them very quickly. As an example, playing the piano and singing, it's like I queue up a line of words in my mind to sing, then switch instantly back to whatever my fingers need to do. You just get very good at switching between things. Which is actually multi-tasking, even as the scientist in the story uses the word.

The people in the story didn't seem to be switching. They were presented with moderately uncommon tasks, and from the MRI it appears they didn't actually switch, they were keeping everything in their mind the whole time, It is well known that you can only keep seven things or so in your mind at the same time, so this is not surprising. If they hadn't used the MRI then this story would have been utterly uninteresting, but even as it is, I don't think the facts of the study supports the author's conclusions.

PS To avoid a headache have you tried giving more sugar to your brain? Bobby Fischer used to drink fruit juice during chess games to help keep up his concentration.

Re:Oh no !

[Taco Cowboy]

Yes, you are chewing gum while listening to music and posting to Slashdot.
How is this multitasking and not slacking?

Task 1: Chewing gum.

10 Chew Gum
20 Goto 10

Task 2: Listening to music

10 Hear Music
20 Shake head
30 Hymn a little bit
40 Shake leg
50 Goto 10

Task 3: Typing to Slashdot

10 Think of words to type
20 Search for the spelling of the word
30 Lift fingers
40 Use right fingers to hit the right keys
50 Eye look at screen
60 Check for typos
70 Check for grammar mistake
80 Goto 10

If that's not multitask, what is?

Re:I used to work on the road...

[lattyware]

Not having an accident doesn't make it safe.

Re:Women can do it better..

[WrongSizeGlass]

So if two is the limit, what does that say about men?
Which head are they thinking with?

I think the answer is obvious. Our two tasks are:
1) Thinking about the woman we're are talking to
2) Thinking about the other woman over there.

Pick two

[characterZer0]

Thinking
Talking
Listening

Pick two.

Re:Pick two

[IANAAC]

If you are an interpreter, you routinely do all three at the same time.

Sorry, just because it's difficult for some doesn't mean it's impossible. It does take training and practice, though.

A victory for the workforce

[sanche]

I'm glad to see this. There are way too many people in my business life claiming to be good at multitasking when their only real strength is never giving anything their full attention.

It takes a certain amount of horsepower for your brain to help you get through a list of tasks, simple or not. When you focus, you get those things done faster, and usually at a higher quality.

Windows XP Starter Edition

[K. S. Kyosuke]

So the three-app limit in Windows XP was scientifically justified!

A Minority Can Multitask

[sonicmerlin]

I recall an article at Arstechnica about cell phone use while driving mentioning a study that found a minority of people are actually capable of multi-tasking while the rest are "bad at it". Oh yes, here we go:

http://arstechnica.com/science/news/2010/03/rare-supertaskers-balance-driving-and-cellphone-use.ars

Obviously...

[ThoughtMonster]

...all the researchers are men and have never met any women.

Re:Women can do it better..

[geekmux]

Somewhere not so long ago I saw research article that pointed out women can multi-task better than men. And that it was a trait of women in general.

Its a matter of dealing with kids.

So if two is the limit, what does that say about men? Which head are they thinking with?

My apologies if I call bullshit here. A "matter of dealing with kids" is your proof? And the women who don't have kids?

It used to be that mens car insurance rates were MUCH higher than womens. Perhaps you should take a closer look at the rates today, since women think they can drive, put on makeup, and talk on the phone at the same time, and the insurance rates prove it. So does the side of my car.

Re:Oh no !

[Taco Cowboy]

Isn't your last task really two tasks in one? I mean what're your left fingers doing eh??

Ahem, a delicate observation. Of course, it could mean you used your right (as opposed to wrong) fingers, but who knows what a slashdotter means

Mea Culpa.

Should have used the word "correct" instead of the word "right".

Sorry !

Re:OMG! Is that BASIC I see???

[Taco Cowboy]

Wait till you see I use the "gosub" command ! Muahahahaha !

Practice

[TheLink]

Seriously though, you might be able to learn how to do that if you could practice doing that 100 times every day, for a month under safe simulated conditions (e.g. driving simulator, and simulated eating too, otherwise you'd end up killing yourself by overeating ;) ).

It's all about practice. Practice, practice, practice.

The first time you drive a car (especially a manual), there are so many tasks.

After a while of practice, your brain configures itself to automatically make those tasks into a subtask, and groups them all into one task - "driving".

Of course some people may never be able to do it. But I think a high proportion of people can. And I bet there are some people who can learn to do it after very short time - just like some people can learn to juggle very quickly, and there was that recent article about supertaskers.

I'm sure Michael Schumacher can eat breakfast and type on a cellphone and still do F1 laps faster than I can, when I'm just doing F1 laps (just driving, not eating or doing other stuff).

The trouble with most people is they're trying to do "for real" without practicing _properly_. That's like trying to juggle chainsaws, without learning how to juggle balls first, and then gradually working your way up under controlled conditions.

Re:Practice

[raynet]

I would think driving a bus while texting or eating would be even more dangerous.

Re:Practice

[mdarksbane]

Just from my own experience, it seems like there are a bunch of different things going on when you try to multitask.

There are things you have practiced so much that your brain no longer has to think about them - like say, walking, or driving when there are no changes in the road or other cars. Let's call these "background processes" although in terms of computer architecture it's more like you've delegated the work to a specialized unit like a GPU. I can generally walk and do multiple things at once with the conscious part of your brain. The thing is that this requires the background process to be both well=practiced and unchanging. If the road ahead of you is empty, you can drive for miles without really consciously thinking about the road, sometimes even missing your exit by miles without realizing it. But if a deer jumps out or someone cuts in front of you, that part of your processing can't handle it, and you have to go back to the active part quickly or you're going to crash.

I've also noticed something like what this article is talking about, where it seems like you're processing things in parallel, sort of like a multi-core system. You're just doing two active thinking things at once. Some people are better than others at this. Personally, when thinking in this mode, I have a hard time handling more than two things or so, as this article says I should, and my performance in both those tasks decreases. I've also noticed that certain types of tasks are harder to do this with - I only seem to be able to have one input and one output stream open at a time. Have you ever failed at talking to someone on the phone while writing something else (or listening to your wife while also reading slashdot)? If you're actively processing both at the same time, it can be pretty hard.

But this is where I get to what people never seem to mention when they talk about multitasking, which is how I personally handle greater than 2 things at once. It's like a time-slicing model. There is a (sometimes large) portion of my attention that is thinking nothing but "do this task, then do this next task, then go back to this other task." Sometimes it's shorter slices than others. Like with the wife and slashdot model - I have to listen, then read a sentence while she pauses, then go back to listening. You sort of jump between each task quickly, get it back to a steady state, then jump to your other task and try to do some work on it before the last one needs attention again. As long as I am focusing on the multitasking queue and not too much on any individual task, I can do a lot of things this way, and I think it's how most people end up handling large numbers of tasks. The problem is first that there is a lot of overhead, and second that if you end up locking onto one task (and starving your scheduling thread, essentially) you can not realize how much time has passed and let the other tasks all go to shit. This is more of the driver who talks on his cell phone but is still actively paying attention to the road (instead of just going on autopilot) and will therefore occasionally miss bits of the conversation or shift lanes later than he is supposed to because he's thinking about remembering both of them.

Does that sound familiar to anyone? Just realized that model has been floating in my head for forever, but I don't know if anyone else thinks that way.

Re:Practice

[TheLink]

1) You don't need full situational awareness[1] while driving to be safer than the average driver. If we ever are going to officially allow some drivers to multitask, there better be a driving test where people have to prove that they are much better than the average driver while multitasking. Then we ( the average drivers) are far more likely to kill them than the other way round ;). I'd prefer it if every driver was required to take that test, even if they can't pass it (and don't have to for a normal license) - it's a good thing to try to make most of us know how crappy we are at driving.

2) Don't do multiple dangerous tasks at once. That way you can drop the other tasks if "stuff happens". The trouble is even with a hands-free kit, too many people are too stupid[2] to just shut-up and drive when stuff gets dangerous.

[1] There are zillions of things a driver can be aware of which can improve safety, but we don't require all of them to drive better than average. The average driver does not look for toddler/animal feet under parked cars, and prepare to brake. So many drivers don't even seem to look many cars ahead for potential issues (prepare to change lanes well before the problem). And you can easily learn to do this sort of stuff even if you are talking to someone else (if you can't multitask, just stop talking, do stuff, resume talking).

[2] I saw a video where a sword swallower said he had a bad accident when a bird sat on his shoulder unexpectedly. To me that shows he is very bad at prioritization for him to do what he does safely. When you have a sword swallowed in your throat, you do NOT turn your head no matter what. It's like the "pain box" test in Dune.

Re:Practice

[Cylix]

I am little more concerned at the apparent theft of a vehicle. I hope there were at least no passengers on board.

The type of task matters

[Webz]

In my opinion, the type of task matters. And I think it has to do with what parts of your brain are used. For example, I can code/refactor and listen to a podcast just fine simultaneously. But if it's two comprehension-based tasks, like reading AND listening, I can't do them. Or lately I've even noticed I can't mentally elaborate on a thought and listen to a podcast at the same time.

The coding and listening thing seems very left brain/right brain to me.

Also, to the poster that mentioned musical multi-tasking... That's really interesting! But I think it helps that we as musicians have been training since a very young age to accept that level of multi-tasking, so the things that become muscle memory do. Fingering, breathing, sight reading, etc. Really the only thing that matters by show time is watching the conductor, the rest should be on semi auto pilot.

Re:No. Just, no.

[dominious]

There is an example from R. Feynman, where he said he used to count the time in his head but he could not talk at the same time, whereas someone else could do that easily but he could not read a paper at the same time. OTOH Feynman could read the newspaper while counting time.

What was the difference? Feynman was counting time by narrating the numbers in his head (using the speech system), while the other guy was picturing the numbers in his head (using the image system). So if he was using the speech system he could not speak at the same time because that system was already in use, while the other guy could not read because he was already using the image system.

Re:I can verify it's true

[ultranova]

I had an accident and the zone of my brain which is responsible for the communication between the two hemispheres of the brain (corpus callosum) was damaged during a important head injury. Now it's difficult to take notes while listening to a speaker for example because I need to concentrate on two tasks.

Can the "other" hemisphere act on its own? I mean, is it more like having lost half your brain, or having been split into two beings in a single body?

So both hemispheres need to work actively but what is more important is the communication between them

Yes. I theorize that in order to meld separate nodes to a single entity, the communication between them has to be at least as fast as information processing within them. That way they stay so well synchronized and coordinated that they are, for all intents and purposes, a single entity - a brain, rather than just a bunch of neurons.

This is important for AI research, since it implies that the current design of computers - fast processor, but huge cost of communication and cache misses - is as bad fit for AI as can be. Instead, you'd want lots and lots and lots of relatively weak cores with their own dedicated on-chip memory and capability of sending messages to each other.

I wonder if graphis cards and compute shaders would fit the bill? They certainly are much better at parallelization. Of course, even then you'd need lots and lots and lots of them...

Or just run the whole thing over the Internet. Let's add AI nodes to various P2P programs and see Skynet emerge :). Seriously, the burden on a single computer would be pretty low, so it should be technically doable...

I was a drummer

[AnonymousClown]

Playing a drumset requires both wrists and both feet moving, seemingly, at different times..

It's really all one thing - one movement. In other words, my wrists and feet where acting synchronously to the beat. The position for each body part would be different but the timing was the same. Probably the most impressive drummer I've ever heard was Omar Hakim - drummed for Sting on "Dream of the Blue Turtles". Sometimes I wonder if that guy's hemispheres actually communicate. Which makes me wonder of those folks whose hemispheres were disconnected wouldn't be awesome drummers or piano players.

Re:OMG! Is that BASIC I see???

[PopeRatzo]

Why does 2010 require so many empty parentheses?

I would think that in 2010 it would look more like this:

1. Slide to Unlock

2. Chew Gum App (Free Version)

3. Click!

Are you sure?

[louzerr]

I'm not sure if I ... hang on, that's my phone ... I'm not sure if I ... hold on, I've got an IM. But the study ... dammit! I give up!

Every one else is bragging...

[P-Nuts]

So many posts bragging about being able to do a million different things at once. I don't think I can do two things at once. Once I get going I need a hardware interrupt to stop me. Usually it's the "desperately need to piss" interrupt.

Re:OMG! Is that BASIC I see???

[mswhippingboy]

Typical iPhad response. 3 sequential steps and call it multitasking :)
Oh wait, I forgot, iPhad can only multitask 2 tasks (one builtin app and one 3rd Party app). No, background notifications don't count. If interrupt handling is considered multitasking, then msdos was a multitasking beast (I wrote many TSR apps back in the day).
Full disclosure: I'm writing this on my iPhad so don't peg me as anti-apple (I have 4 more iPhads I'm paying for for wife&kids). I'm supporting Apple more than any shill so I will speak my mind.
The last time I made a remark critical of apple I got modded troll so I'm aware of the iGod followers here.
If this draws a troll mod, then I say F U moderator.

Doing 4 tasks right now? Can you beat it?

[AmigaHeretic]

This is bogus. Watching porn, masturbating, a cigarette in my mouth, and I'm still able to type this message with my other hand.

That's 4. Can anyone beat that?

Re:Bundling?

[TheLink]

> Things like "fiddle with radio" or "adjust GPS" still feel like a separate task, no matter how many times I do it.

How many times have you actually _practiced_ it? You can't just do it a few times a day to get better at it. It has to become like walking to you, so that you don't think of the separate things to do to fiddle with the radio. You just think "radio channel #1" and it happens - the rest of your brain goes and does it.

That said, some people never ever learn how to fly a conventional helicopter no matter how much they try and practice.

And I guess most people will never get this good at tetris even if they practiced a lot:

http://www.youtube.com/watch?v=jwC544Z37qo

Skip to about 2:50 and watch till the end where the "locked" blocks go invisible...

He can probably play normal tetris while driving and talking on the phone. I'm assuming he can learn how to drive ;).

Re:Doing 4 tasks right now? Can you beat it?

[iamhassi]

No one wants to beat that

Re:Doing 4 tasks right now? Can you beat it?

[orangesquid]

When you practice doing two tasks simultaneously, they become a new, single task. How do good drummers play syncopated beats? You learn a multitude of "keeping the beat" tasks involving many combinations of common patterns on the bass drum, hi-hat, and ride cymbal, then you learn a variety of syncopated beat tasks to play "overtop" of the other task. (You also have to learn strategies for performing these tasks at the same time, especially when you have to borrow a foot or hand from the keeping-the-beat task for an accentuated part and then un-borrow it; however, my point---namely, for a good drummer, many complex patterns involving multiple limbs, when practiced sufficiently, become simply "one task"---still stands.)

Re:ADD/ADHD people would disagree

[Renraku]

It's more about switching tasks than it is doing tasks at once. Imagine a normal person having to stack their working papers neatly, put them in a drawer with a file, and then close the drawer, every time they wanted to think about something not directly related to the task they're doing. For ADD people, they can actually just throw the papers on the desk or still hold them while answering the phone.

Studies show that it takes about 5-10 minutes of work to get back into the flow of things and work at peak efficiency. A noisy phone ringing or baby crying will start this timer over again. ADD people can pick it up within a minute or a few seconds, but they have trouble doing one simple task all day.

Re:OMG! Is that BASIC I see???

[mswhippingboy]

I'm sorry if this went past you. Let me explain this to you s l o w l y...
iPhad is a play off of the iPhone & iPad platform with a double meaning. Remember "double entendre" from grade school?
Say iPhad very slowly several times and maybe you'll get it - but then again maybe not.
I don't even know why I'm responding to an AC (that's Anonymous Coward if you need an explanation of that as well), but since you appear to need spoon feeding; if you'll pay attention, posts on /. are initially set to Score:1 and either modded up or down - or ignored (in which case they stay Score:1) - by the moderators.
However, I don't post here for the scores. I do it because I enjoy participating in the (occasional) interesting discussions and even the (more frequent) jousting of ideas and points of view.
I will say though, posting as an AC will not garner you much respect because it shows you don't have the guts to put your identity behind your comment.