Apr 16 2012

Multitasking – Can You Walk and Chew Gum at the Same Time?

Multitasking – the act of doing more than one thing at the same time – is largely an illusion. You can’t do it, at least not well. The research over the last couple of decades has shown in numerous ways how difficult and wasteful attempting to multitask is. Now a new study purports to show a possible benefit to multitasking. I will get to that study later – first, let’s review how bad multitasking is.

Researchers believe that there is a processing bottleneck in the brain. Essentially, we don’t have multi-core processors with multi-threading. In neurological terms, there are various functional components to consider. One is executive function, which is the “supervisor” function in the frontal lobes. Executive function includes the process of focusing attention, allocating resources, coordinating information, and scheduling cognitive tasks. Everything that the brain does is a finite resource, including executive function.

Attention itself is also limited. Our attention can be spread out so that we are taking in a lot of information at once, although very superficially. In this mode we may be scanning our environment for something interesting, or something in particular, but missing a lot of detail. Or we may focus our attention down on one thing, taking in greater detail but at the expense of ignoring everything else. This spreading out or narrowing down of our attention applies no only to sensory input but also ideas.

Some researchers believe that there are different information processing modes that we can engage in – either divergent or convergent. Divergent thinking allows us to look at the whole picture and integrate different pieces of information. Convergent thinking, however, is for deep systematic thinking on one topic.

So there are different ways in which we can focus our attention and different modes of information processing. There are also different specific pieces of information we can focus on, or sensory inputs, and of course there are different cognitive tasks to which we can turn our attention. I mention all of this because this is at the core of the difficulty with multitasking – switching among different types and targets of attention and information processing.

We cannot literally perform two cognitive tasks simultaneously. Rather, we switch between them (or among three or more tasks). Every time we switch our attention or our cognitive style that uses executive function resources (which are finite). Such tasks may also use resources of memory retrieval and other limited brain resources. Therefore some of our limited resources are being allocated just to switching tasks, and are therefore not available to engage in those tasks themselves.

This phenomenon is referred to as interference – one task interfering with performance on another. This interference can often be bidirectional – both tasks interfere with each other.

This definitely accords with my personal experience. If I am engaged in a mental task I prefer to have minimal distractions. If I am trying to also do something else at the same time (perhaps I am checking e-mail while writing a blog, for example) I waste time just just getting back mentally to where I was before I switched tasks. I end up taking more time to complete both tasks than if I did them separately, and the incidence of mistakes goes way up.

To use another computer analogy – sometimes, because I am impatient, if my computer is taking a long time to complete a task I may open another window and work on something else. Making the computer perform two processing-intensive tasks simulaneously takes more time than if both tasks were done alone, because the computer now has to expend resources loading information into memory and accessing the hard drive as it is switching resources from one task to the other (assuming you are using a computer that does not have true multitasking ability).

What I have summarized so far is all pretty basic. Researchers in this area are drilling down deeper to some interesting questions. For example, it is established that if we are performing a task that requires us to perceive certain information, that other information that is not related to the task will cause distraction and reduce performance (through interference). If, however, the task is using up all of our perceptual capacity (so-called high perceptual load), then there won’t be any perceptual capacity left over to notice the distracting events, and interference will paradoxically disappear. In every day terms – if you are fully engaged in a complex task you may “block out” distractions in your environment. Your brain simply won’t have the capacity to process those distractions.

This is only true, however, for tasks that are perceptually demanding. Tasks that are demanding in other ways, such as being memory intensive or involving stimuli that are at the edge of perception (things that are very small, for example) do not display this high-load phenomenon of causing interference to disappear.

There also appears to be an ongoing debate about perceptual interference being “early” or “late”. The early interference view is that distractions keep us from processing task-specific information at all – they interfere early in the process of perception. The late interference hypothesis is that the early processing of sensory stimuli is obligatory, and that distractions interfere with later processing of that perceived information. I haven’t read enough to have an opinion about which hypothesis is more likely to be true, and this appears to still be a point of controversy.

At this point you may be saying, “Wait a minute. I can walk and chew gum at the same time, and it doesn’t seem that my gum chewing suffers as a result.” This is due to what is called automaticity. Some tasks, like walking, inherently use little cognitive resources. This is because they utilize sub-cortical more primitive and subconscious parts of the brain. Our brain stems (the most primitive part of the brain) perform much of the processing necessary for simple walking. The brain stem also regulates other automatic functions, like breathing, which is why you don’t have to concentrate very hard in order to breath.

Learned tasks may also become more and more automatic over time. That is part of the benefit of practice. The cerebellum, for example, can learn coordinated motor actions, like shooting baskets, and can take over for our higher cognitive functions.

Automaticity, therefore, does not alter the reality of multitasking, but it does reduce the amount of cognitive resources that a task requires, and so the negative effects of multitasking are diminished. Both chewing gum and walking are tasks with high automaticity, which is the reason for the cliche insult in the first place.

The new study has to do with a special category of multitasking called media multitasking – looking at TV while texting a friend and watching a YouTube video on your iPad, for example. Research has shown consistent differences in information processing between high media multitaskers (HMMs) and low media multitaskers (LMMs). This research shows that HMMs perform worse on attentional tasks than LMMs. Specifically HMMs tend to maintain a wider attentional scope, even when instructed to focus on something specific, and therefore perform worse on tasks that require a narrow attentional scope.

This makes sense, although there does not appear to be any data that helps separate out cause and effect. Do HMMs learn to maintain a wider attentional scope, or are people who tend to have a wider attentional scope drawn to media multitasking? In fact, HMMs tend to be ironically worse at multitasking, because their wide attentional scope makes them more distractable and they suffer greater interference when task switching.

The new study is interesting because it set out to find if there is any task at which HMMs have an advantage. They separate subjects into groups of HMMs and LMMs and then gave them two different tasks.  The subjects had to find a target shape on a computer screen among similar shapes. In one version of the task there was also a sound that drew attention to the target shape, in another version there was no sound. Similar to previous research, the HMMs did worse than the LMMs on the target finding task without the sound. They were worse at filtering out task-irrelevant stimuli. However, they performed better than the LMMs when the sound was present.

The thinking here is that HMMs are better at integrating multiple sensory inputs. This may be the first study to find a cognitive advantage to HMMs. It does make a certain superficial sense – media multitasking often involves paying attention to multiple difference kinds of sensory input at once.

Again – this study did not address cause and effect, so we are left not knowing if this potential advantage of integrating multiple sensory inputs is learned by HMMs or causes people to gravitate toward being an HMM. This is also (standard caveats) a single smallish study that needs to be replicated.


The human brain does not appear to be evolved for multitasking. Our brains have finite resources that have to be divided among the tasks in which we engage. Many societies, however, seem to be moving toward greater and greater multitasking demands. More and more people are becoming HMMs, whether they want to or not.

The unintended consequence of our information-heavy multimedia society is that we may be creating a generation of people who maintain a wide scope of attention so as to take in all of the sensory information with which they are bombarded. However, this comes at the expense of being able to focus attention on a single task and filter out distractions. The result is that most cognitive tasks suffer (including, ironically, multitasking itself).

If the results of the current study are reliable and hold up to replication, it seems there may be some advantages to media multitasking, specifically in the ability to integrate different streams of sensory input. The net effect of all this still needs to be sorted out. It seems, however, that if we want to mitigate the effects of heavy media multitasking we need to either reduce it, or design tasks that take advantage of the benefits and mitigate the weaknesses.

I do wonder if this is just a phase we are going through. Will future generations look back at the early 21st century and marvel at the ridiculous media multitasking. It may seem as if we are in the adolescence of using media technology, and later generations will be more mature and will understand the need to control our media exposure. We need to resist the temptation to extrapolate current trends indefinitely into the future – in other words, we should not assume that future generations will be even more heavily multimedia consumers. In addition to simply becoming more mature in this respect, technology may throw another curve ball in the mix and change the way we consume media in ways we cannot currently predict.

Either way, this is research worth following and a trend worth keeping one eye on – although not necessarily while engaging in other tasks.



17 responses so far

17 thoughts on “Multitasking – Can You Walk and Chew Gum at the Same Time?”

  1. SARA says:

    I can’t think of a practical task that involves integrating multiple sensory inputs. So I’m still thinking the HMM is at a distinct disadvantage to the LLM.

    I think I am an LLM, because I feel so slow and stupid when I try to multi-task compared to “these young kids today.”

    I’m surprised to learn that those who I would guess to be HHM are actually not good at mutlitaksing. I perceive them to be so. They perceive themselves to be so. They spend so much time taking in 3 or 4 media inputs at a time, that it seems like they would be entirely non-functional if they weren’t good at it.

    I also think that as I age, I am getting far worse at multi tasking media options. I can no longer even listen to music and read. And I used to do that constantly in my teens and 20’s.

  2. ccbowers says:

    “I’m surprised to learn that those who I would guess to be HHM are actually not good at mutlitaksing. I perceive them to be so. They perceive themselves to be so.”

    That last sentence is important. It appears that people are often unaware of how poorly they accomplish tasks while multitasking. I find this very strange, because it seems very obvious to me. Then again this may be because I am a person who enjoys focusing on topics, one at a time. Only recently have I been shifting to the HMM lifestyle.

  3. Dirk Steele says:

    Well while I was watching the telly and eating my dinner I happened to glance at this blog report from my facebook recommendations whilst sending birthday greetings to my friends reminders. Thinking that it was about time I retrieved the hoover from wherever I had used it last, and put on the washing machine so that I had clean clothes for my important interview tomorrow, I had a little time to reflect again on what Dr. Novella was trying to say. But then I was distracted….

  4. SARA says:

    # Rikki-Tikki-Tavi – Navigating Traffic. Of course. Why didn’t I think of that?

    On your other thought, I would not imagine that there would be a difference between men and women in multi-tasking (or multi-tasking interference, more accurately), is there a study that shows it is possible?

  5. bsoo says:

    There are times when I’m working on a problem and then take a break to work on another task. After working on the other task for a while, sometimes I will think of the solution to the problem I was previously working on even though I wasn’t consciously thinking about it. We must be using cognitive resources for both tasks, so it seems we are capable of true multi-tasking (beyond automatic behaviors), but to expand on the computer metaphor, we can only have one task in the foreground at a time.

  6. nybgrus says:

    I have known this personally for a while now. I was once self deluded into thinking I could multitask effectively.

    Nowadays I just focus on one topic to the exclusion of others when I need to get it done and done well. If I do multitask, or HMM, I do so knowing that no task I am doing will be done as well, that it will take me longer, and I prioritize which task I want/need to have more attention towards.

    Like right this moment my girlfriend will be starting up a movie and I will be reading some lectures on orthopedics. I know my reading will suffer, but I don’t want to be an orthopod, so I accept it. However, I need to retain most of it, so it will get the majority of my attention and whatever movie she puts on will essentially remain unwatched for me.

  7. Donna B. says:

    #Sara & Rikki-Tikki-Tavi — driving a car is a great example because it also involves automaticity. In heavy traffic, attention is devoted to which car is trying to plow into yours, while on a rural interstate attention can be devoted to scenery or cows. Or trying to figure out if that car up ahead is highway patrol.

    For me, any competing sensory input involving words is more distracting. I can read while some bland instrumental music is playing, but have never (even in my teen years) been able to read when lyrics are involved. This applies to lyrics I know even if the version I’m hearing is instrumental.

    I absolutely abhor the placement of TVs tuned to news or talk shows in public areas where I have to wait (hospital and doctor waiting rooms and airports specifically). I’ve always got a book with me that I’d rather read. It’s quite easy for me to tune out the buzz of multiple normal conversations.

    This is (one reason) why I don’t think I would be a good police officer even though I think I’m a decent driver. I’d be overwhelmed trying to listen to the scanner and look for specific things like somebody wearing a mask running away from a bank. You probably wouldn’t want someone like me piloting aircraft either.

    Dang, I’m feeling sort of useless now :/

  8. Bart says:

    Theres only 1 thing that can truly be multi-tasked, and thats kicking ass and chewing bubble gum, unless you are out of bubble gum

  9. Shelley says:

    A couple of things come to mind about this subject. The first is that there was a study several years ago (sorry no access to it at the moment and can’t remember the precise details), that essentially demonstrated that students perform better on exams when they write the exam under the same type of conditions in which they studied for them.

    I was teaching a course at the time and remember joking with colleagues that this suggested that we should test students while they are highly fatigued, caffeine loaded, with music blasting from the classroom speakers. In alll seriousness, however, this study of HMMs vs LMMs would suggest something similar. Students who study for exams while checking Facebook, email, and listening to music would seem likely to perform less well on exams than those who can (and do) study in a quiet environment – regardless of whether they know the material equally well.

    The other thought has to do with the issue of the automaticity that takes over for higher cognitive functions: the fact that we can perform some functions while on ‘automatic’ doesn’t mean that we necessarily perform our best that way. In professional sports, for example, players must raise their level of attention via anxiety or becoming hyped up by coaches etc in order to overcome the tendency to play on automatic. They need to intentionally overcome that well-rehearsed automaticity so they can give a great performance. So, automaticity likely has a significant downside when the quality of the performance is critical.

  10. RichWilson says:

    I kept waiting for some mention of cell phones and driving. I am stunned/freaked/scared at the number of people I see who still drive, and talk, or even fiddle with their devices. We have simulator data that says using a cell phone significantly impairs driving, but we don’t seem to yet have a lot of real world crash data correlated to device use.

  11. nybgrus says:

    very good point RichWilson.

    That is why I think that hands free laws are asinine. The issue is not the fact that you can’t drive one handed. Or that it is incredibly complex to simply hold a phone to your head. The issue is that the content of the call is quite distracting from driving.

    Of course, for an average mundane call, I think there isn’t much issue. The automaticity of driving lends itself well to that. Most likely you will just go on “auto-pilot” and drive home instead of the store, if anything at all. However, if the conversation is intense, complex, emotional, etc… then it is indeed quite dangerous.

    But nothing is quite as dangerous as texting and driving. Thankfully my phone takes dictation and sends texts/emails by voice command.

  12. ccbowers says:

    “That is why I think that hands free laws are asinine. The issue is not the fact that you can’t drive one handed. Or that it is incredibly complex to simply hold a phone to your head. The issue is that the content of the call is quite distracting from driving.”

    Of course they are nonsensical, but it allows politicians to look like they are doing something about a problem. Banning cell phones altogether would appear to be extreme by the average person.
    I disagree that the average mundane call is not problematic. I agree that intense conversations are worse, but even mundane calls will slow reaction time enough to make a big difference… its not so much about going the wrong route as it is: not stopping in time if traffic ahead stops quickly, or if a car pulls out in front of you suddenly, or if a kid runs into the road.

  13. ccbowers says:

    “But nothing is quite as dangerous as texting and driving. Thankfully my phone takes dictation and sends texts/emails by voice command.”

    One side effect of cracking down in this is that people will text below the line of sight of the road so their phones are not seen by other drivers (police). This eliminates the possibility of identifying danger with their peripheral vision. I’m not saying that texting higher up so that you can “see” the road is a good thing, I just wonder if it is now worse

  14. Lissie says:

    The irony was not at all lost on me that I was reading this blog post at the same time as studying for my biology exam

  15. floam says:

    Would it be more accurate to refer to what most people call multitasking as multiplexing?

  16. FNTC says:

    So we are all shutting the door on our ability to multi-task? I think we are forgetting about the brains ability to respond to training. I cannot see why plasticity with learning to do two things at once would be any different to the changes the brain takes after reaching expertise in single task skills.

    Granted, learning to do two things at once, depending on what they are may take alot of practice. but look at the walking and chewing gum example; we are all conceding that we can do these automatically, but then saying that this is only because they utilise subcortical areas. Well ofcourse – we’ve done it since we were very young, and therefore had a lot of practice. its been shown that once a task reaches automaticity that we sub-cortical areas become more involved in chunking motor sequences.

Leave a Reply