<p>First, it is important to disambiguate between <em>concurrent multitasking</em> and <em>sequential multitasking</em> (<a href="https://doi.org/10.1145/1518701.1518981" rel="nofollow noreferrer">Salvucci et al, 2009</a>). In a recent publication I present a short overview on related work of both (<a href="https://doi.org/10.1016/j.chb.2016.03.059" rel="nofollow noreferrer">Jeuris and Bardram, 2016</a>):</p>

<blockquote>
  <p>During concurrent multitasking cognitive resources have to be divided across several competing parallel tasks, such as driving while talking on the phone. Many ‘dual-task’ studies investigate dual-task interference and reduction of performance while performing two simultaneous tasks. ...</p>
  
  <p>In contrast to concurrent multitasking, sequential multitasking denotes the interleaving of several primary tasks which are executed one at a time. ... Studies investigating sequential multitasking are among other things interested in measuring the effects of task interleaving on productivity and accuracy.
  ...</p>
  
  <p>Results show an inverted U-relationship between multitasking and productivity; there is thus an optimal amount of task switching which leads to the highest productivity. However, increased levels of multitasking lead to a significant loss in accuracy, indicating a trade-off between productivity and accuracy (<a href="https://doi.org/10.1016/j.ijhcs.2011.10.003" rel="nofollow noreferrer">Adler &amp; Benbunan-Fich, 2012</a>). </p>
</blockquote>

<p>In regards to the effect of <em>task difficulty</em> on sequential multitasking, "subjective task difficulty has been found to be a determining factor: easy tasks benefit from multitasking by increasing stimulation, whereas hard tasks decrease performance as the result of an overload in mental workload (<a href="http://doi.org/10.1093/iwc/iwu005" rel="nofollow noreferrer">Adler &amp; Benbunan-Fich, 2015</a>)".</p>

<p>So to answer your question, at least one study has found that for the tasks they used more challenging tasks do 'suffer' more from multitasking. However, there is still an optimum amount of multitasking.</p>

<p><sub>
Salvucci, D. D., Taatgen, N. A., &amp; Borst, J. P. (2009, April). <a href="https://doi.org/10.1145/1518701.1518981" rel="nofollow noreferrer">Toward a unified theory of the multitasking continuum: From concurrent performance to task switching, interruption, and resumption.</a> In Proceedings of the SIGCHI conference on human factors in computing systems (pp. 1819-1828). ACM.<br>
Jeuris, S., &amp; Bardram, J. E. (2016). <a href="https://doi.org/10.1016/j.chb.2016.03.059" rel="nofollow noreferrer">Dedicated workspaces: Faster resumption times and reduced cognitive load in sequential multitasking.</a> Computers in Human Behavior, 62, 404-414.<br>
Adler, R. F., &amp; Benbunan-Fich, R. (2015). <a href="http://doi.org/10.1093/iwc/iwu005" rel="nofollow noreferrer">The effects of task difficulty and multitasking on performance.</a> Interacting with Computers, 27(4), 430-439.<br>
Adler, R. F., &amp; Benbunan-Fich, R. (2012). <a href="https://doi.org/10.1016/j.ijhcs.2011.10.003" rel="nofollow noreferrer">Juggling on a high wire: Multitasking effects on performance.</a> International Journal of Human-Computer Studies, 70(2), 156-168.
</sub></p>

CC BY-SA 3.0
2017-10-06T06:48:32.460Z
+ 1 very good references. I interpret the "optimum amount of multitasking" as multitasking without any significant effects on performance or error rate.
DesignerAnalyst
CC BY-SA 3.0
2017-10-06T08:14:47.753Z
The inverted U-relationship in Adler 2012 refers to productivity only (progress made on the tasks), thus not taking errors into account. I believe accuracy was more linearly correlated. Obviously 'optimum' would depend highly on task type:  e.g., the potential impact of 'errors'.
Steven Jeuris
CC BY-SA 3.0
2017-10-05T13:25:16.590Z
2017-10-05T13:41:48.800Z
2017-10-05T13:41:48.800Z
Steven Jeuris
<p>The effects of multitasking are apparent even for the most trivial tasks. For example try walking and eating a sandwich at the same time, you will walk slower and more irregular. The multitasking effects though, are much less when the competing tasks are simple or familiar.</p>

<p>Exctract from <a href="http://www.apa.org/research/action/multitask.aspx" rel="nofollow noreferrer">this article</a> :</p>

<blockquote>
  <p>In experiments published in 2001, Joshua Rubinstein, PhD, Jeffrey
  Evans, PhD, and David Meyer, PhD, conducted four experiments in which
  young adults switched between different tasks, such as solving math
  problems or classifying geometric objects. For all tasks, the
  participants lost time when they had to switch from one task to
  another. <strong>As tasks got more complex, participants lost more time</strong>. As a
  result, people took significantly longer to switch between more
  complex tasks. Time costs were also greater when the participants
  switched to tasks that were relatively unfamiliar. They got up to
  speed faster when they switched to tasks they knew better.</p>
</blockquote>

<p>Reference:</p>

<p><a href="http://umich.edu/~bcalab/documents/RubinsteinMeyerEvans2001.pdf" rel="nofollow noreferrer">Rubinstein, J. S., Meyer, D. E. &amp; Evans, J. E. (2001). Executive Control of Cognitive Processes in Task Switching. Journal of Experimental Psychology: Human Perception and Performance, 27, 763-797.</a></p>

CC BY-SA 3.0
2017-10-05T13:28:26.060Z
The study you reference is a 'task switching' study, not exactly the same as your example of "walking and eating a sandwich at the same time". E.g., see [Salvucci et al., 2009](https://dl.acm.org/citation.cfm?doid=1518701.1518981). These types of studies are more interested in the effects of e.g. switching between different 'types' of 'task sets' (e.g., recognizing a number as odd or even, a character as a vowel or consonant). Although insightful to understand limitations of executive function and such, the degree to which this says something about 'higher-level' multitasking is questionable.
Steven Jeuris
CC BY-SA 3.0
2017-10-06T06:35:15.527Z
@StevenJeuris even concurrent tasks involves some rapid switching, the central executive can work with only one thing at a time. Nevertherless I agree that multitasking is a very complex phenomenon with many factors like modality, familiarity, rapid/slow switching, sharing resources, motivation etc and we have to be cautious with any absolute generalization. However I tend to believe that even multitasking on trivial  tasks has some minor effects. Here is some [additional reference](https://psychology.uiowa.edu/hazelab/dual-task-interference) focusing on modality and practise.
DesignerAnalyst
CC BY-SA 3.0
2017-10-05T06:23:27.030Z
2017-10-05T06:23:27.030Z
DesignerAnalyst
<p>How does the efficiency of multi-tasking differ by task type? My understanding is that multitasking impairs efficiency for cognitively challenging tasks.</p>

<p>Does this apply to trivial tasks as well?</p>

CC BY-SA 3.0
2017-10-04T20:43:40.347Z
Welcome. How would you define *cognitively challenging* and *impaired efficiency*? Their quite subjective things. Basically it seems that you ask whether simple and complicated tasks both reduce task efficiency? Did you do any prior research? Can you share where you are at at this stage?
AliceD
CC BY-SA 3.0
2017-10-05T12:51:17.477Z
Citations on where your current understanding comes from are also appreciated. ;p I have studied this topic extensively and can likely provide you with an answer, but first I need to know what _type_ of multitasking you are referring to. _Concurrent multitasking_ (as in doing two things at the same time), or more long-term intertwining of tasks, frequently switching from one to the other over the course of minutes-hours?
Steven Jeuris
CC BY-SA 3.0
2017-10-05T13:40:23.780Z
In addition, 'efficiency' could also be clarified. In [my answer](https://cogsci.stackexchange.com/a/18225/21) I presumed you intend more 'typical' multitasking in everyday work (sequential multitasking) and efficiency in terms of impact on the performed work.
Steven Jeuris
<cognitive-neuroscience><performance><cognition><neuropsychology>
Efficiency of multitasking depending on task difficulty
user16520
# Efficiency of multitasking depending on task difficulty

(Asked by: username_0 on 2017-10-04)

How does the efficiency of multi-tasking differ by task type? My understanding is that multitasking impairs efficiency for cognitively challenging tasks.

Does this apply to trivial tasks as well?

**Tags:** cognitive-neuroscience, performance, cognition, neuropsychology

> **Comments:**
> **username_1**: Welcome. How would you define *cognitively challenging* and *impaired efficiency*? Their quite subjective things. Basically it seems that you ask whether simple and complicated tasks both reduce task efficiency? Did you do any prior research? Can you share where you are at at this stage?  
> **username_2**: Citations on where your current understanding comes from are also appreciated. ;p I have studied this topic extensively and can likely provide you with an answer, but first I need to know what _type_ of multitasking you are referring to. _Concurrent multitasking_ (as in doing two things at the same time), or more long-term intertwining of tasks, frequently switching from one to the other over the course of minutes-hours?  
> **username_2**: In addition, 'efficiency' could also be clarified. In [my answer](https://cogsci.stackexchange.com/a/18225/21) I presumed you intend more 'typical' multitasking in everyday work (sequential multitasking) and efficiency in terms of impact on the performed work.  

---

## 2 answers

### Answer by username_2 on 2017-10-05. Score: 5

First, it is important to disambiguate between *concurrent multitasking* and *sequential multitasking* ([Salvucci et al, 2009](https://doi.org/10.1145/1518701.1518981)). In a recent publication I present a short overview on related work of both ([Jeuris and Bardram, 2016](https://doi.org/10.1016/j.chb.2016.03.059)):

> During concurrent multitasking cognitive resources have to be divided across several competing parallel tasks, such as driving while talking on the phone. Many ‘dual-task’ studies investigate dual-task interference and reduction of performance while performing two simultaneous tasks. ...
>
> In contrast to concurrent multitasking, sequential multitasking denotes the interleaving of several primary tasks which are executed one at a time. ... Studies investigating sequential multitasking are among other things interested in measuring the effects of task interleaving on productivity and accuracy.
> ...
>
> Results show an inverted U-relationship between multitasking and productivity; there is thus an optimal amount of task switching which leads to the highest productivity. However, increased levels of multitasking lead to a significant loss in accuracy, indicating a trade-off between productivity and accuracy ([Adler & Benbunan-Fich, 2012](https://doi.org/10.1016/j.ijhcs.2011.10.003)).

In regards to the effect of *task difficulty* on sequential multitasking, "subjective task difficulty has been found to be a determining factor: easy tasks benefit from multitasking by increasing stimulation, whereas hard tasks decrease performance as the result of an overload in mental workload ([Adler & Benbunan-Fich, 2015](http://doi.org/10.1093/iwc/iwu005))".

So to answer your question, at least one study has found that for the tasks they used more challenging tasks do 'suffer' more from multitasking. However, there is still an optimum amount of multitasking.

Salvucci, D. D., Taatgen, N. A., & Borst, J. P. (2009, April). [Toward a unified theory of the multitasking continuum: From concurrent performance to task switching, interruption, and resumption.](https://doi.org/10.1145/1518701.1518981) In Proceedings of the SIGCHI conference on human factors in computing systems (pp. 1819-1828). ACM.  
Jeuris, S., & Bardram, J. E. (2016). [Dedicated workspaces: Faster resumption times and reduced cognitive load in sequential multitasking.](https://doi.org/10.1016/j.chb.2016.03.059) Computers in Human Behavior, 62, 404-414.  
Adler, R. F., & Benbunan-Fich, R. (2015). [The effects of task difficulty and multitasking on performance.](http://doi.org/10.1093/iwc/iwu005) Interacting with Computers, 27(4), 430-439.  
Adler, R. F., & Benbunan-Fich, R. (2012). [Juggling on a high wire: Multitasking effects on performance.](https://doi.org/10.1016/j.ijhcs.2011.10.003) International Journal of Human-Computer Studies, 70(2), 156-168.

> **Comments:**
> **username_3**: + 1 very good references. I interpret the "optimum amount of multitasking" as multitasking without any significant effects on performance or error rate.  
> **username_2**: The inverted U-relationship in Adler 2012 refers to productivity only (progress made on the tasks), thus not taking errors into account. I believe accuracy was more linearly correlated. Obviously 'optimum' would depend highly on task type:  e.g., the potential impact of 'errors'.  

---

### Answer by username_3 on 2017-10-05. Score: 1

The effects of multitasking are apparent even for the most trivial tasks. For example try walking and eating a sandwich at the same time, you will walk slower and more irregular. The multitasking effects though, are much less when the competing tasks are simple or familiar.

Exctract from [this article](http://www.apa.org/research/action/multitask.aspx) :

> In experiments published in 2001, Joshua Rubinstein, PhD, Jeffrey
> Evans, PhD, and David Meyer, PhD, conducted four experiments in which
> young adults switched between different tasks, such as solving math
> problems or classifying geometric objects. For all tasks, the
> participants lost time when they had to switch from one task to
> another. **As tasks got more complex, participants lost more time**. As a
> result, people took significantly longer to switch between more
> complex tasks. Time costs were also greater when the participants
> switched to tasks that were relatively unfamiliar. They got up to
> speed faster when they switched to tasks they knew better.

Reference:

[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, 763-797.](http://umich.edu/~bcalab/documents/RubinsteinMeyerEvans2001.pdf)

> **Comments:**
> **username_2**: The study you reference is a 'task switching' study, not exactly the same as your example of "walking and eating a sandwich at the same time". E.g., see [Salvucci et al., 2009](https://dl.acm.org/citation.cfm?doid=1518701.1518981). These types of studies are more interested in the effects of e.g. switching between different 'types' of 'task sets' (e.g., recognizing a number as odd or even, a character as a vowel or consonant). Although insightful to understand limitations of executive function and such, the degree to which this says something about 'higher-level' multitasking is questionable.  
> **username_3**: @StevenJeuris even concurrent tasks involves some rapid switching, the central executive can work with only one thing at a time. Nevertherless I agree that multitasking is a very complex phenomenon with many factors like modality, familiarity, rapid/slow switching, sharing resources, motivation etc and we have to be cautious with any absolute generalization. However I tend to believe that even multitasking on trivial  tasks has some minor effects. Here is some [additional reference](https://psychology.uiowa.edu/hazelab/dual-task-interference) focusing on modality and practise.  

---

