In 2013 I reported how a 3-second interruption while doing a task doubled the rate of sequence errors, while a 4s one tripled it. A new study has attempted to measure just how much ongoing interruptions can negatively affect the quality of a complex creative task.

The study involved 54 students who were given 12 minutes to outline and 12 minutes to write a short essay on an assigned topic. One group was interrupted multiple times with an unrelated task during outlining, while another group was interrupted repeatedly during the writing stage, and a control group had no interruptions.

The quality of the essay produced was significantly lower in both interruption conditions (an average score of 3.06 for the writing-interruption group, and 3.13 for the outline-interruption group, compared to 3.71 for the control group). The number of words produced was significantly lower when the student was interrupted during writing (282 words vs the control group's 315 words), but not when interrupted during outlining (307 words).

Essay quality was assessed by independent graders using a 6-point scale. The interruptions occurred every three minutes and lasted one minute, during which the student was asked to complete an arithmetic problem or word puzzle (this time wasn't included in the 12 minutes).

A follow-up experiment in which the time given was lengthened to 20 minutes, and interruptions occurred at random intervals, produced similar results, although the overall scores were slightly higher.

[3869] Foroughi, C. K., Werner N. E., Nelson E. T., & Boehm-Davis D. A.
(2014).  Do Interruptions Affect Quality of Work?.
Human Factors: The Journal of the Human Factors and Ergonomics Society. 56(7), 1262 - 1271.

Three recent studies point to the impact of social media and multiple device use on learning and cognitive control.

College students take years to learn to manage their social media so it doesn't impact their grades

A survey of 1,649 college students has found that freshmen average a total of two hours a day on Facebook, of which over an hour is spent also doing schoolwork, and that time spent on Facebook had a negative impact on their grade point average. For sophomores and juniors, only time spent using Facebook while doing schoolwork affected their GPA.

Seniors spent the least time on Facebook, the least time multitasking on Facebook, and their time on Facebook didn't affect their grades.

It's suggested that the difference between the year-groups has to do with the way the students interact with Facebook, and in particular, the students' ability to self-regulate.

Internet use during class impacts grades no matter how smart you are

An investigation into non-academic Internet use during an introductory psychology class has found that all students, regardless of their intellectual ability, were negatively affected by greater Internet use, with lower exam scores the more they used the Internet.

Not surprisingly (given other research showing that students are notoriously bad at appreciating good strategies or recognizing poor ones), the students themselves discounted such effects on their learning.

The study involved some 500 students, and used self-reports of internet use.

Given that this is an introductory class, we can safely assume most are freshmen.

Brain scans reveal 'gray matter' differences in media multitaskers

A brain imaging study involving 75 adults has found that, independent of individual personality traits, people who frequently use several media devices at the same time had smaller grey matter density in the anterior cingulate cortex than those who use just one device occasionally. Functional connectivity between the ACC and the precuneus was also negatively affected.

The ACC is critical for cognitive and emotional control.

While it is possible that people with a smaller ACC are more likely to engage in such multitasking, the findings are consistent with other research showing that building expertise also builds gray matter in the relevant brain region (e.g., London taxi drivers building up the part of their hippocampus that deals with navigation), while gray matter can also shrink with disuse.

The findings are also consistent with evidence that individuals who engage in heavier media-multitasking perform more poorly on cognitive control tasks and exhibit more socio-emotional difficulties.

There's both positive and negative news in these reports:

positive, that students can eventually learn how to control their media multitasking (though the question occurs: is there a correlation between the students who drop out and those who can't learn the requisite cognitive control?)

negative, that failing to learn the requisite control may push the student into a negative feedback cycle, with their cognitive control network being eroded the more they continue to media multitask.

The negative scenario becomes even more likely for some individuals when you realize that those with the poorest control are unlikely to recognize their problem:

Poor multitaskers don't realize it

In 2013, I reported that college students who scored highest in multitasking ability were least likely to multitask, while those who scored lowest were most likely to engage in it. Last year, another study came out telling us that, while people generally realize that multitasking impairs performance, those who are worse at it don't realize it.

The study involved 69 volunteers who were given a visual tracking task, in which they had to keep a mouse cursor within a small target that moved erratically around a circular track. They also separately performed an auditory n-back task (a challenging working memory task). Before being asked to perform both tasks at the same time, they were asked to predict how much their performance would be affected.

Most people overestimated how much their performance would suffer. However, there was no correlation at all between individual predictions and performance, and those who were most affected showed no awareness that they were poorer than average at multitasking.

[3870] Junco, R.
(2015).  Student class standing, Facebook use, and academic performance.
Journal of Applied Developmental Psychology. 36, 18 - 29.

[3873] Ravizza, S. M., Hambrick D. Z., & Fenn K. M.
(2014).  Non-academic internet use in the classroom is negatively related to classroom learning regardless of intellectual ability.
Computers & Education. 78, 109 - 114.

[3872] Loh, K. Kee, & Kanai R.
(2014).  Higher Media Multi-Tasking Activity Is Associated with Smaller Gray-Matter Density in the Anterior Cingulate Cortex.
PLoS ONE. 9(9), 

[3868] Finley, J. R., Benjamin A. S., & McCarley J. S.
(2014).  Metacognition of multitasking: How well do we predict the costs of divided attention?.
Journal of Experimental Psychology: Applied. 20(2), 158 - 165.

I’ve reported often on the perils of multitasking. Here is yet another one, with an intriguing new finding: it seems that the people who multitask the most are those least capable of doing so!

The study surveyed 310 undergraduate psychology students to find their actual multitasking ability, perceived multitasking ability, cell phone use while driving, use of a wide array of electronic media, and personality traits such as impulsivity and sensation-seeking.

Those who scored in the top quarter on a test of multitasking ability tended not to multitask. Some 70% of participants thought they were above average at multitasking, and perceived multitasking ability (rather than actual) was associated with multitasking. Those with high levels of impulsivity and sensation-seeking were also more likely to multitask (with the exception of using a cellphone while driving, which wasn’t related to impulsivity, though it was related to sensation seeking).

The findings suggest that those who multitask don’t do so because they are good at multitasking, but because they are poor at focusing on one task.

In my book on remembering intentions, I spoke of how quickly and easily your thoughts can be derailed, leading to ‘action slips’ and, in the wrong circumstances, catastrophic mistakes. A new study shows how a 3-second interruption while doing a task doubled the rate of sequence errors, while a 4s one tripled it.

The study involved 300 people, who were asked to perform a series of ordered steps on the computer. The steps had to be performed in a specific sequence, mnemonically encapsulated by UNRAVEL, with each letter identifying the step. The task rules for each step differed, requiring the participant to mentally shift gears each time. Moreover, task elements could have multiple elements — for example, the letter U could signal the step, one of two possible responses for that step, or be a stimulus requiring a specific response when the step was N. Each step required the participant to choose between two possible responses based on one stimulus feature — features included whether it was a letter or a digit, whether it was underlined or italic, whether it was red or yellow, whether the character outside the outline box was above or below. There were also more cognitive features, such as whether the letter was near the beginning of the alphabet or not. The identifying mnemonic for the step was linked to the possible responses (e.g., N step – near or far; U step — underline or italic).

At various points, participants were very briefly interrupted. In the first experiment, they were asked to type four characters (letters or digits); in the second experiment, they were asked to type only two (a very brief interruption indeed!).

All of this was designed to set up a situation emulating “train of thought” operations, where correct performance depends on remembering where you are in the sequence, and on producing a situation where performance would have reasonably high proportion of errors — one of the problems with this type of research has been the use of routine tasks that are generally performed with a high degree of accuracy, thus generating only small amounts of error data for analysis.

In both experiments, interruptions significantly increased the rate of sequence errors on the first trial after the interruption (but not on subsequent ones). Nonsequence errors were not affected. In the first experiment (four-character interruption), the sequence error rate on the first trial after the interruption was 5.8%, compared to 1.8% on subsequent trials. In the second experiment (two-character interruption), it was 4.3%.

The four-character interruptions lasted an average of 4.36s, and the two-character interruptions lasted an average of 2.76s.

Whether the characters being typed were letters or digits made no difference, suggesting that the disruptive effects of interruptions are not overly sensitive to what’s being processed during the interruption (although of course these are not wildly different processes!).

The absence of effect on nonsequence errors shows that interruptions aren’t disrupting global attentional resources, but more specifically the placekeeping task.

As I discussed in my book, the step also made a significant difference — for sequence errors, middle steps showed higher error rates than end steps.

All of this confirms and quantifies how little it takes to derail us, and reminds us that, when engaged in tasks involving the precise sequence of sub-tasks (which so many tasks do), we need to be alert to the dangers of interruptions. This is, of course, particularly true for those working in life-critical areas, such as medicine.

[3207] Altmann, E. M., Gregory J., & Hambrick D. Z.
(2013).  Momentary Interruptions Can Derail the Train of Thought.
Journal of Experimental Psychology: General. No - Pagination Specified.

I’ve reported, often, on the evidence that multitasking is a problem, something we’re not really designed to do well (with the exception of a few fortunate individuals), and that the problem is rooted in our extremely limited working memory capacity. I’ve also talked about how ‘working memory’ is a bit of a misnomer, given that we probably have several ‘working memories’, for different modalities.

It follows from that, that tasks that use different working memories should be easier to do at the same time than tasks that use the same working memory. A new study confirms that multitasking is more difficult if you are trying to use the same working memory modules for both tasks.

In the study, 32 students carried out a visual pattern-matching task on a computer while giving directions to another person either via instant messaging (same modalities — vision and motor) or online voice chat (different modality — hearing).

While both simultaneous tasks significantly worsened performance on the pattern-matching task, communicating by IM (same modality) led to a 50% drop in visual pattern-matching performance (from a mean of 11 correct responses to a mean of 5), compared to only a 30% drop in the voice condition (mean of 7).

The underlying reason for the reductions in performance seems to be in the effect on eye movement: the number and duration of eye fixations was reduced in both dual-task conditions, and more so in the IM condition.

Note that this is apparently at odds with general perception. According to one study, IM is perceived to be less disruptive than the phone. Moreover, in the current study, participants felt they performed better in the IM condition (although this palpably wasn’t true). This feeling may reflect the greater sense of personal control in instant messaging compared to chat. It may also reflect an illusion of efficiency generated by using the visual channel — because we are so strongly practiced in using vision, we may find visual tasks more effortless than tasks using other modalities. (I should note that most people, regardless of the secondary task, felt they did better than they had! But those in the IM condition were more deluded than those in the chat condition.)

The finding also explains why texting is particularly dangerous when driving — both rely heavily on the same modalities.

All this is consistent with the idea that there are different working memory resources which can operate in parallel, but share one particular resource which manages the other resources.

The idea of ‘threaded cognition’ — of maintaining several goal threads and strategically allocating resources as needed — opens up the idea that multitasking is not all bad. In recent years, we have focused on multitasking as a problem. This has been a very necessary emphasis, given that its downsides were unappreciated. But although multitasking has its problems, it may be that there are trade-offs that come from the interaction between the tasks being carried out.

In other words, rather than condemning multitasking, we need to learn its parameters. This study offers one approach.

Meditation may improve multitasking

I recently reported that developing skill at video action games doesn’t seem to improve general multitasking ability, but perhaps another approach might be more successful. Meditation has, of course, been garnering growing evidence that it can help improve attentional control. A new study extends that research to multitasking in a realistic work setting.

The study involved three groups of 12-15 female human resource managers, of whom one group received eight weeks of mindfulness-based meditation training, another received eight weeks of body relaxation training, and another initially received no training (control), before receiving the mindfulness training after the eight weeks.

Before and after each eight-week period, the participants were given a stressful test of their multitasking abilities, requiring them to use email, calendars, instant-messaging, telephone and word-processing tools to perform common office tasks (scheduling a meeting; finding a free conference room; writing a draft announcement of the meeting, eating snacks and drinking water, writing a memo proposing a creative agenda item for the meeting). Necessary information came from emails, instant messages, telephone calls, and knocks on the door. The participants had 20 minutes to complete the tasks.

The meditation group reported lower levels of stress during the multitasking test compared to the control and relaxation groups. They also spent more time on tasks and switched tasks less often, while taking no longer to complete the overall job than the others. Both meditation and relaxation groups showed improved memory for the tasks they were performing.

After the control group underwent the meditation training, their results matched those of the meditation group.

The meditation training emphasized:

  • control of attentional focus
  • focusing attention in the present moment or task
  • switching focus
  • breath and body awareness.

The relaxation training emphasized progressive tensing and relaxing of major muscle groups, aided by relaxation imagery.

It's interesting that overall time on task didn't change (the researchers remarked that the meditators didn't take any longer, but of course most of us would be looking for it to become shorter!), but I wouldn't read too much into it. The task was relatively brief. It would be interesting to see the effects over the course of, say, a day. Nor did the study look at how well the tasks were done.

But it is, of course, important that meditation training reduced task-switching and stress. Whether it also has a postitive effect on overall time and quality of work is a question for another day.

IBMT improves white matter efficiency

A recent imaging study has found that four weeks of a form of mindfulness meditation called integrative body–mind training (IBMT) improved white matter efficiency in areas surrounding the anterior cingulate cortex, compared to controls given relaxation training.

The anterior cingulate is part of the brain network related to self-regulation. Deficits in activation in this part of the brain have been associated with attention deficit disorder, dementia, depression, schizophrenia, and other disorders.

Using the data from a 2010 study involving 45 U.S. college students, and another involving 68 Chinese students, researchers found that axon density (one factor in white matter efficiency) had improved after two weeks, but not myelin formation. After a month (about 11 hours of meditation), both had improved. Mood improved by two weeks.

Previous studies involving computer-based training for improving working memory have found changes in myelination, but not axon density.

Meditators’ better cognitive control may be rooted in emotional regulation

Previous work has found that people who engage in meditation show higher levels of executive control on laboratory tasks.

An electrical signal called the Error Related Negativity (ERN) occurs in the brain within 100 ms of an error being committed. When meditators and non-meditators were given the Stroop Test, meditators not only tended to do better on the test, but their ERNs were stronger.

The interesting thing about this is that the best performers were those who scored highest on emotional acceptance. Mindful awareness was less important. It’s suggested that meditators may be able to control their behavior better not because of their sharper focus, but because they are more aware of their emotions and regulate them better.

Something to think about!

Levy, D. M., Wobbrock, J. O., Kaszniak, A. W., & Ostergren, M. (2012). The Effects of Mindfulness Meditation Training on Multitasking in a High-Stress Information Environment, 45–52. Full text available at

[3051] Tang, Y-Y., Lu Q., Fan M., Yang Y., & Posner M. I.
(2012).  Mechanisms of white matter changes induced by meditation.
Proceedings of the National Academy of Sciences. 109(26), 10570 - 10574.

[3052] Teper, R., & Inzlicht M.
(2012).  Meditation, mindfulness and executive control: the importance of emotional acceptance and brain-based performance monitoring.
Social Cognitive and Affective Neuroscience.

The research is pretty clear by this point: humans are not (with a few rare exceptions) designed to multitask. However, it has been suggested that the modern generation, with all the multitasking they do, may have been ‘re-wired’ to be more capable of this. A new study throws cold water on this idea.

The study involved 60 undergraduate students, of whom 34 were skilled action video game players (all male) and 26 did not play such games (19 men and 7 women). The students were given three visual tasks, each of which they did on its own and then again while answering Trivial Pursuit questions over a speakerphone (designed to mimic talking on a cellphone).

The tasks included a video driving game (“TrackMania”), a multiple-object tracking test (similar to a video version of a shell game), and a visual search task (hidden pictures puzzles from Highlights magazine).

While the gamers were (unsurprisingly) significantly better at the video driving game, the non-gamers were just as good as them at the other two tasks. In the dual-tasking scenarios, performance declined on all the tasks, with the driving task most affected. While the gamers were affected less by multitasking during the driving task compared to the non-gamers, there was no difference in the amount of decline between gamers and non-gamers on the other two tasks.

Clearly, the smaller effect of dual-tasking on the driving game for gamers is a product of their greater expertise at the driving game, rather than their ability to multitask better. It is well established that the more skilled you are at a task, the more automatic it becomes, and thus the less working memory capacity it will need. Working memory capacity / attention is the bottleneck that prevents us from being true multitaskers.

In other words, the oft-repeated (and somewhat depressing) conclusion remains: you can’t learn to multitask in general, you can only improve specific skills, enabling you to multitask reasonably well while doing those specific tasks.

[3001] Donohue, S., James B., Eslick A., & Mitroff S.
(2012).  Cognitive pitfall! Videogame players are not immune to dual-task costs.
Attention, Perception, & Psychophysics. 74(5), 803 - 809.

Comparison of young adults (mean age 24.5) and older adults (mean age 69.1) in a visual memory test involving multitasking has pinpointed the greater problems older adults have with multitasking. The study involved participants viewing a natural scene and maintaining it in mind for 14.4 seconds. In the middle of the maintenance period, an image of a face popped up and participants were asked to determine its sex and age. They were then asked to recall the original scene.

As expected, older people had more difficulty with this. Brain scans revealed that, for both groups, the interruption caused their brains to disengage from the network maintaining the memory and reallocate resources to processing the face. But the younger adults had no trouble disengaging from that task as soon as it was completed and re-establishing connection with the memory maintenance network, while the older adults failed both to disengage from the interruption and to reestablish the network associated with the disrupted memory.

This finding adds to the evidence that an important (perhaps the most important) reason for cognitive decline in older adults is a growing inability to inhibit processing, and extends the processes to which that applies.

A study involving 125 younger (average age 19) and older (average age 69) adults has revealed that while younger adults showed better explicit learning, older adults were better at implicit learning. Implicit memory is our unconscious memory, which influences behavior without our awareness.

In the study, participants pressed buttons in response to the colors of words and random letter strings — only the colors were relevant, not the words themselves. They then completed word fragments. In one condition, they were told to use words from the earlier color task to complete the fragments (a test of explicit memory); in the other, this task wasn’t mentioned (a test of implicit memory).

Older adults showed better implicit than explicit memory and better implicit memory than the younger, while the reverse was true for the younger adults. However, on a further test which required younger participants to engage in a number task simultaneously with the color task, younger adults behaved like older ones.

The findings indicate that shallower and less focused processing goes on during multitasking, and (but not inevitably!) with age. The fact that younger adults behaved like older ones when distracted points to the problem, for which we now have quite a body of evidence: with age, we tend to become more easily distracted.

Why are other people’s phone conversations so annoying? A new study suggests that hearing only half a conversation is more distracting than other kinds of conversations because we're missing the other side of the story and so can't predict the flow of the conversation. This finding suggests that driving a car might be impaired not only by the driver talking on the phone, but also by passengers talking on their phones.

It also tells us something about the way we listen to people talking — we’re actively predicting what the person is going to say next. This helps explain something I’ve always wondered about. Listen to people talking in a language you don’t know and you’re often amazed how fast they talk. See an audio recording of the soundwaves, and you’ll wonder how people know when one word starts and another begins. Understanding what people are saying is not as easy as we believe it is — it takes a lot of experience. An important part of that experience, it seems, is learning the patterns of people’s speech, so we can predict what’s going to come next.

The study showed that people overhearing cell phone conversations did more poorly on everyday tasks that demanded attention, than when overhearing both sides of a cell phone conversation, which resulted in no decreased performance. By controlling for other acoustic factors, the researchers demonstrated that it was the unpredictable information content of the half-heard conversation that was so distracting.

Emberson, L.L., Lupyan, G., Goldstein, M.H. & Spivey, M.J. 2010. Overheard Cell-Phone Conversations: When Less Speech Is More Distracting Psychological Science first published on September 3, 2010 as doi:10.1177/0956797610382126

While brain training programs can certainly improve your ability to do the task you’re practicing, there has been little evidence that this transfers to other tasks. In particular, the holy grail has been very broad transfer, through improvement in working memory. While there has been some evidence of this in pilot programs for children with ADHD, a new study is the first to show such improvement in older adults using a commercial brain training program.

A study involving 30 healthy adults aged 60 to 89 has demonstrated that ten hours of training on a computer game designed to boost visual perception improved perceptual abilities significantly, and also increased the accuracy of their visual working memory to the level of younger adults. There was a direct link between improved performance and changes in brain activity in the visual association cortex.

The computer game was one of those developed by Posit Science. Memory improvement was measured about one week after the end of training. The improvement did not, however, withstand multi-tasking, which is a particular problem for older adults. The participants, half of whom underwent the training, were college educated. The training challenged players to discriminate between two different shapes of sine waves (S-shaped patterns) moving across the screen. The memory test (which was performed before and after training) involved watching dots move across the screen, followed by a short delay and then re-testing for the memory of the exact direction the dots had moved.

A study assessing the performance of 200 people on a simulated freeway driving task, with or without having a cell phone conversation that involved memorizing words and solving math problems, has found that, as expected, performance on both tasks was significantly impaired. However, for a very few, performance on these tasks was unaffected (indeed their performance on the memory task improved!). These few people — five of them (2.5%) — also performed substantially better on these tasks when performed alone.

Watson, J.M. & Strayer, D.L. 2010. Supertaskers: Profiles in extraordinary multitasking ability. Psychonomic Bulletin and Review. In Press.

Full text is available at

As we all know, being interrupted during a task greatly increases the chance we’ll go off-kilter (I discuss the worst circumstances and how you can minimize the risk of mistakes in my book Planning to remember). Medication errors occur as often as once per patient per day in some settings, and around one-third of harmful medication errors are thought to occur during medication administration. Now an in-depth study involving 98 nurses at two Australian teaching hospitals over 505 hours has revealed that at least one procedural failure occurred in 74.4% of administrations and at least one clinical failure in 25%. Each interruption was associated with a 12.1% increase in procedural failures and a 12.7% increase in clinical errors. Procedural failures include such errors as failure to check patient's identification, record medication administration, use aseptic technique; clinical failures such errors as wrong drug, dose, or route. Interruptions occurred in over half of the 4000 drug administrations. While most errors were rated as clinically insignificant, 2.7% were considered to be major errors — and these were much more likely to occur after interruptions, particularly after repeated interruptions. The risk of major error was 2.3% when there was no interruption; this rose to 4.7% with four interruptions. Nurse experience provided no protection against making a clinical error and was associated with higher procedural failure rates (this is common with procedural failures — expertise renders you more vulnerable, not less).

Older news items (pre-2010) brought over from the old website

Improving your multitasking skills

Teaching older brains to regain youthful skills

Researchers have succeeded in training seniors to multitask at the same level as younger adults. Over the course of two weeks, both younger and older subjects learned to identify a letter flashed quickly in the middle of a computer screen and simultaneously localize the position of a spot flashed quickly in the periphery as well as they could perform either task on its own. The older adults did take longer than the younger adults to reach the same level of performance, but they did reach it.

[571] Richards, E., Bennett P. J., & Sekuler A. B.
(2006).  Age related differences in learning with the useful field of view.
Vision Research. 46(25), 4217 - 4231.

Age and individual differences

Teen's ability to multi-task develops late in adolescence

A study involving adolescents between 9 and 20 years old has found that the ability to multi-task continues to develop through adolescence. The ability to use recall-guided action to remember single pieces of spatial information (such as looking at the location of a dot on a computer screen, then, after a delay, indicating where the dot had been) developed until ages 11 to 12, while the ability to remember multiple units of information in the correct sequence developed until ages 13 to 15. Tasks in which participants had to search for hidden items in a manner requiring a high level of multi-tasking and strategic thinking continued to develop until ages 16 to 17. "These findings have important implications for parents and teachers who might expect too much in the way of strategic or self-organized thinking, especially from older teenagers."

[547] Luciana, M., Conklin H. M., Hooper C. J., & Yarger R. S.
(2005).  The Development of Nonverbal Working Memory and Executive Control Processes in Adolescents.
Child Development. 76(3), 697 - 712.

About multitasking

Stress disrupts task-switching, but the brain can bounce back

A new neuroimaging study involving 20 male M.D. candidates in the middle of preparing for their board exams has found that they had a harder time shifting their attention from one task to another after a month of stress than other healthy young men who were not under stress. The finding replicates what has been found in rat studies, and similarly correlates with impaired function in an area of the prefrontal cortex that is involved in attention. However, the brains recovered their function within a month of the end of the stressful period.

[829] Liston, C., McEwen B. S., & Casey B. J.
(2009).  Psychosocial stress reversibly disrupts prefrontal processing and attentional control.
Proceedings of the National Academy of Sciences. 106(3), 912 - 917.

Full text available at

Asymmetrical brains let fish multitask

A fish study provides support for a theory that lateralized brains allow animals to better handle multiple activities, explaining why vertebrate brains evolved to function asymmetrically. The minnow study found that nonlateralized minnows were as good as those bred to be lateralized (enabling it to favor one or other eye) at catching shrimp. However, when the minnows also had to look out for a sunfish (a minnow predator), the nonlateralized minnows took nearly twice as long to catch 10 shrimp as the lateralized fish.

[737] Dadda, M., & Bisazza A.
(2006).  Does brain asymmetry allow efficient performance of simultaneous tasks?.
Animal Behaviour. 72(3), 523 - 529.

How much can your mind keep track of?

A recent study has tried a new take on measuring how much a person can keep track of. It's difficult to measure the limits of processing capacity because most people automatically break down large complex problems into small, manageable chunks. To keep people from doing this, therefore, researchers created problems the test subjects wouldn’t be familiar with. 30 academics were presented with incomplete verbal descriptions of statistical interactions between fictitious variables, with an accompanying set of graphs that represented the interactions. It was found that, as the problems got more complex, participants performed less well and were less confident. They were significantly less able to accurately solve the problems involving four-way interactions than the ones involving three-way interactions, and were completely incapable of solving problems with five-way interactions. The researchers concluded that we cannot process more than four variables at a time (and at that, four is a strain).

[415] Halford, G. S., Baker R., McCredden J. E., & Bain J. D.
(2005).  How many variables can humans process?.
Psychological Science: A Journal of the American Psychological Society / APS. 16(1), 70 - 76.

We weren't made to multitask

A new imaging study supports the view that we can’t perform two tasks at once, rather, the tasks must wait their turn — queuing up for their turn at processing.

[1070] Jiang, Y., Saxe R., & Kanwisher N.
(2004).  Functional magnetic resonance imaging provides new constraints on theories of the psychological refractory period.
Psychological Science: A Journal of the American Psychological Society / APS. 15(6), 390 - 396.

Why multitasking is a problem

Talking, walking and driving with cell phone users

Another cellphone-multitasking study! Compared with people walking alone, in pairs, or listening to their ipod, cell phone users were the group most prone to oblivious behavior: only 25% of them noticed a unicycling clown passing them on the street, compared to 51% of single individuals, 61% of music player users, and 71% of people in pairs. In fact, cell phone users even had problems walking — walking more slowly, changing direction more often, being prone to weaving, and acknowledging other people more rarely.

Hyman, I.E.Jr, Boss, S. M., Wise, B. M., McKenzie, K. E., & Caggiano, J. M. (2009). Did you see the unicycling clown? Inattentional blindness while walking and talking on a cell phone. Applied Cognitive Psychology, 9999(9999), n/a. doi: 10.1002/acp.1638.

Chronic media multitasking correlated with poor attention

Media multitasking — keeping tabs on email, texts, IM chat, the web — is routine among young people in particular. We know that humans can’t really multitask very successfully — that what we do is switch tracks, and every time we do that there’s a cost, in terms of your efficiency at the task. But what about long-term costs of chronic multitasking? A study that selected 19 students who multitasked the most and 22 who multitasked least, from a pool of 262 students, found those who multitasked least performed better on three cognitive tests that are thought to reflect ability to ignore distracting information, ability to organize things in working memory, and ability to switch between tasks. The findings can’t answer whether chronic media multitasking reduces these abilities, or whether people who are poor at these skills are more likely to succumb to chronic media multitasking, but they do demonstrate that chronic media multitasking is associated with this particular information processing style.

[890] Ophir, E., Nass C., & Wagner A. D.
(2009).  From the Cover: Cognitive control in media multitaskers.
Proceedings of the National Academy of Sciences. 106(37), 15583 - 15587.

Cell phone ringtones can pose major distraction, impair recall

Cell phones ringing during a concert is not simply irritating. It appears that in a classroom, a cell phone left to ring for 30 seconds significantly affected the students’ recall for the information presented just prior to and during the ringing. The effect was even greater when the phone’s owner rummaged frantically through her bag. Ringtones that are popular songs were even greater distractions. However, with repeated trials, people could be trained to reduce the negative effects; being warned about the distracting effects also helped people be less affected.

[1299] Shelton, J. T., Elliott E. M., Eaves S. D., & Exner A. L.
(2009).  The distracting effects of a ringing cell phone: An investigation of the laboratory and the classroom setting.
Journal of Environmental Psychology. 29(4), 513 - 521.

Police with higher multitasking abilities less likely to shoot unarmed persons

In a study in which police officers watched a video of an officer-involved shooting that resulted in the death of the officer before participating in a computer-based simulation where they were required to make split-second decisions whether to shoot or not to shoot someone, based on slides showing a person holding either a gun or a harmless object like a cell phone, it was found that among those more stressed by the video, those with a lower working memory capacity were more likely to shoot unarmed people. Working memory capacity was not a significant factor for those who did not show heightened negative emotionality in response to the video.

[739] Kleider, H. M., Parrott D. J., & King T. Z.
(2009).  Shooting behaviour: How working memory and negative emotionality influence police officer shoot decisions.
Applied Cognitive Psychology. 9999(9999), n/a - n/a.

Switchboard in the brain helps us learn and remember at the same time

It’s very common that we are required to both process new information while simultaneously recalling old information, as in conversation we are paying attention to what the other person is saying while preparing our own reply. A new study confirms what has been theorized: that there is a bottleneck in our memory system preventing us from doing both simultaneously. Moreover, the study provides evidence that a specific region in the left prefrontal cortex can resolve the bottleneck, possibly by allowing rapid switching between learning and remembering. This is supported by earlier findings that patients with damage to this area have problems in rapidly adapting to new situations and tend to persevere in old rules. The same region is also affected in older adults.

[1355] Huijbers, W., Pennartz C. M., Cabeza R., & Daselaar S. M.
(2009).  When Learning and Remembering Compete: A Functional MRI Study.
PLoS Biol. 7(1), e1000011 - e1000011.

Full text is available at

Neural bottleneck found that thwarts multi-tasking

An imaging study has revealed just why we can’t do two things at once. The bottleneck appears to occur at the lateral frontal and prefrontal cortex and the superior frontal cortex. Both areas are known to play a critical role in cognitive control. These brain regions responded to tasks irrespective of the senses involved, and could be seen to 'queue' neural activity — that is, a response to the second task was postponed until the response to the first was completed. Such queuing occurred when two tasks were presented within 300 milliseconds of each other, but not when the time gap was longer.

[896] Dux, P. E., Ivanoff J., Asplund C. L., & Marois R.
(2006).  Isolation of a Central Bottleneck of Information Processing with Time-Resolved fMRI.
Neuron. 52(6), 1109 - 1120.

How multitasking impedes learning

A number of studies have come out in recent years demonstrating that the human brain can’t really do two things at once, and that when we do attempt to do so, performance is impaired. A new imaging study provides evidence that we tend to use a less efficient means of learning when distracted by another task. In the study, 14 younger adults (in their twenties) learned a simple classification task by trial-and-error. For one set of the cards, they also had to keep a running mental count of high tones that they heard while learning the classification task. Imaging revealed that different brain regions were used for learning depending on whether the participants were distracted by the other task or not — the hippocampus was involved in the single-task learning, but not in the dual-task, when the striatum (a region implicated in procedural and habit learning) was active. Although the ability of the participants to learn didn’t appear to be affected at the time, the distraction did reduce the participants' subsequent knowledge about the task during a follow-up session. In particular, on the task learned with the distraction, participants could not extrapolate from what they had learned.

[1273] Foerde, K., Knowlton B. J., & Poldrack R. A.
(2006).  Modulation of competing memory systems by distraction.
Proceedings of the National Academy of Sciences. 103(31), 11778 - 11783.

Doing two things at once

Confirmation of what many of us know, and many more try to deny - you can't do two complex tasks simultaneously as well as you could do either one alone. Previous research has showed that when a single area of the brain, like the visual cortex, has to do two things at once, like tracking two objects, there is less brain activation than occurs when it watches one thing at a time. This new study sought to find out whether something similar happened when two highly independent tasks, carried out in very different parts of the brain, were done concurrently. The two tasks used were language comprehension (carried out in the temporal lobe), and mental rotation (carried out in the parietal lobe). The language task alone activated 37 voxels of brain tissue. The mental rotation task alone also activated 37 voxels. But when both tasks were done at the same time, only 42 voxels were activated, rather than the sum of the two (74). While overall accuracy did not suffer, each task took longer to perform.

[2546] Just, M A., Carpenter P. A., Keller T. A., Emery L., Zajac H., & Thulborn K. R.
(2001).  Interdependence of Nonoverlapping Cortical Systems in Dual Cognitive Tasks.
NeuroImage. 14(2), 417 - 426.

The costs of multitasking

Technology increasingly tempts people to do more than one thing (and increasingly, more than one complicated thing) at a time. New scientific studies reveal the hidden costs of multitasking. In a study that looked at the amounts of time lost when people switched repeatedly between two tasks of varying complexity and familiarity, it was found that for all types of tasks, subjects lost time when they had to switch from one task to another, and time costs increased with the complexity of the tasks, so it took significantly longer to switch between more complex tasks. Time costs also were greater when subjects switched to tasks that were relatively unfamiliar. They got "up to speed" faster when they switched to tasks they knew better. These results suggest that executive control involves two distinct, complementary stages: goal shifting ("I want to do this now instead of that") and rule activation ("I'm turning off the rules for that and turning on the rules for this").

[1124] Rubinstein, J. S., Meyer D. E., & Evans J. E.
(2001).  Executive Control of Cognitive Processes in Task Switching,.
Journal of Experimental Psychology: Human Perception and Performance. 27(4), 763 - 797.

Brain's halves compete for attention

Claus Hilgetag, of Boston University, and his colleagues fired focused magnetic pulses through healthy subjects' skulls for 10 minutes to induce 'hemispatial neglect'. This condition, involving damage to one side of the brain, leaves patients unaware of objects in the opposite half of their visual field (which sends messages to the damaged half of the brain). The subjects showed the traditional symptoms of hemispatial neglect. They were worse at detecting objects opposite to the numb side of their brain, and worse still if there was also an object in the functioning half of the visual field. Yet numbed subjects were better at spotting objects with the unaffected half of their brains. This behavior confirms the idea that activity in one half of the brain usually eclipses that in the opposite half. The finding supports the idea that mental activity is a tussle between the brain's many different areas.

[720] Hilgetag, C. C., Theoret H., & Pascual-Leone A.
(2001).  Enhanced visual spatial attention ipsilateral to rTMS-induced 'virtual lesions' of human parietal cortex.
Nat Neurosci. 4(9), 953 - 957.

Multitasking and driving

Why cell phones and driving don't mix

A host of studies have come out in recent years demonstrating that multitasking impairs performance and talking on a cell phone while driving a car is a bad idea. A new study helps explain why. In two different experiments, subjects were found to be four times more distracted while preparing to speak or speaking than when they were listening. The researcher expects the effect to be even stronger in real-life conversation. It was also found that subjects could complete the visual task in front of them more easily when the projected voice also was in front. This suggests that it may be easier to have all things that require attention in the same space.

[1132] Almor, A.
(2008).  Why Does Language Interfere with Vision-Based Tasks?.
Experimental Psychology (formerly "Zeitschrift für Experimentelle Psychologie"). 55(4), 260 - 268.

Talking on a cellphone while driving as bad as drinking

Yet another study has come out rubbing it in that multitasking comes with a cost, and most particularly, that you shouldn’t do anything else while driving. This study demonstrates — shockingly — that drivers are actually worse off when using a cell phone than when legally drunk. The study had 40 volunteers use a driving simulator under 4 different conditions: once while legally intoxicated, once while talking on a hands-free cell phone, once while talking on a hand-held cell phone, and once with no distractions. There were differences in behavior —drunk drivers were more aggressive, tailgated more, and hit the brake pedal harder; cell phone drivers (whether hands-free and hand-held ) took longer to hit the brakes, and got in more accidents. But in both cases drivers were significantly impaired.

[1250] Strayer, D. L., Drews F. A., & Crouch D. J.
(2006).  A Comparison of the Cell Phone Driver and the Drunk Driver.
Human Factors: The Journal of the Human Factors and Ergonomics Society. 48(2), 381 - 391.,,1809549,00.html

Performing even easy tasks impairs driving

In yet another demonstration that driving is impaired when doing anything else, a simulator study has found that students following a lead car and instructed to brake as soon as they saw the illumination of the lead car's brake lights, responded slower when required to respond to a concurrent easy task, where a stimulus - either a light flash in the lead car's rear window or an auditory tone - was randomly presented once or twice and participants had to indicate the stimulus' frequency. The finding suggests that even using a hands-free device doesn’t make it okay to talk on a cell phone while driving.

[837] Levy, J., Pashler H., & Boer E.
(2006).  Central interference in driving: is there any stopping the psychological refractory period?.
Psychological Science: A Journal of the American Psychological Society / APS. 17(3), 228 - 235.

Talking and listening impairs your ability to drive safely

A study involving almost 100 students driving virtual cars has provided evidence that people have greater difficultly maintaining a fixed speed when performing tasks that simulated conversing on a mobile phone. Both speaking and listening were equally distracting.

[203] Kubose, T. T., Bock K., Dell G. S., Garnsey S. M., Kramer A. F., & Mayhugh J.
(2006).  The effects of speech production and speech comprehension on simulated driving performance.
Applied Cognitive Psychology. 20(1), 43 - 63.

Cell phone users drive like seniors

Another study on the evils of multitasking, in particular, of talking on a cellphone while driving. This one has a nice spin — the study found that when young motorists talk on cell phones, they drive like elderly people, moving and reacting more slowly and increasing their risk of accidents. Specifically, when 18- to 25-year-olds were placed in a driving simulator and talked on a cellular phone, they reacted to brake lights from a car in front of them as slowly as 65- to 74-year-olds who were not using a cell phone. Although elderly drivers became even slower to react to brake lights when they spoke on a cell phone, they were not as badly affected as had been expected. An earlier study by the same researchers found that motorists who talk on cell phones are more impaired than drunken drivers with blood alcohol levels exceeding 0.08.

[339] Strayer, D. L., & Drew F. A.
(2004).  Profiles in Driver Distraction: Effects of Cell Phone Conversations on Younger and Older Drivers.
Human Factors: The Journal of the Human Factors and Ergonomics Society. 46(4), 640 - 649.

Complex mental tasks interfere with drivers' ability to detect visual targets

The researchers studied 12 adults who drove for about four hours on the highway north from Madrid. During the journey, drivers listened to recorded audio messages with either abstract or concrete information (acquisition task), and later were required to freely generate a reproduction of what they had just listened to (production task). Although the more receptive tasks – listening and learning -- had little or no effect on performance, there were significant differences in almost all of the measures of attention when drivers had to reproduce the content of the audio message they had just heard. Drivers also performed other tasks, either live or by phone. One was mental calculus (mentally changing between Euros and Spanish pesetas) either with an experimenter in the car, talking to the driver, or with the driver speaking by hands-free phone. One was a memory task (giving detailed information about where they were and what they were doing at a given day and time). Both tasks significantly impacted on the driver's ability to detect visual targets. In the experimental variation that examined the impact of hands-free phone conversation, message complexity made the difference. The relative safety of low-demand phone conversation -- if hands-free and voice-operated --appeared to be about the same as that of live conversation. The findings also confirm that the risk of internal distraction (one’s own thoughts) is at least as relevant as external distraction.

Goldarecena, M.A.R. & González, L.M.N. 2003. Mental Workload While Driving: Effects on Visual Search, Discrimination and Decision Making. Journal of Experimental Psychology: Applied, 9(2)