What are the usability benefits of using multiple monitors?

Question

I've read a lot of articles suggesting that work patterns are more effective when using more than one monitor. But why is that the case, from an HCI perspective?

And as follow-up questions, are there any serious downsides to using multiple monitors, and (presuming they do increase usability overall) is there any upper limit to the number of monitors before usability is impaired?

Answer 1

As you rightfully pointed out there are a lot of articles which mention the increase in productivity levels. To quote this Computer Services Auckland Blog - Pulse IT Blog

A University of Utah and ATI Technologies survey of 108 university & non university personnel using Dual Screen monitors reported increases of productivity with 33% fewer errors, 16% faster edits, 6% quicker access to tasks, as well as usability benefits of 45% easier task tracking, 32% faster performance and 24% more comfortable to use than single monitor set ups. Production of work was of a better quality, performed faster and with fewer errors. Task focus of the user along with their speed and ease of learning were also increased.

A survey undertaken for Apple on its larger high definition 30in Cinema screen in comparison to using smaller monitors also offered statistics boasting at least a 45% increase in productivity across the board. This was then disputed as inhumanly possible by one productivity expert who stated that a 5% increase was a more likely figure for larger screen use and around a 30% increase in productivity potential for Dual Monitor use. Although it’s advantageous to having more space to work, it will help some more than others depending on what they are working on. Larger screens could also have positive health benefits for workers such as less eye squinting.

Another white paper by Dell also highlights why users find dual or multiple monitors useful

On a scale of 1-10, Wichita study participants ranked dual monitors as more useful than single screens

There is also an interesting paper by Microsoft research titled Toward Characterizing the Productivity Benefits of Very Large Displays which has this to say about the usability of using large monitors and larger screen space

We did observe several usability issues for both display size conditions. For the small display, there were many problems observed in terms of managing the level of complexity on the small screen, including losing files by accidentally closing them, wasting time resizing for each stage of a task, moving windows so that they weren't occluding key information, etc. From our windows event monitoring software, we observed that users on the small display wasted time bringing windows back to the front when occluded, resizing and repositioning them. In addition, small display users spent extra time accidentally opening and closing documents they did not intend to because the taskbar aggregated window items by application (i.e., all open web pages would collapse to one tile on the taskbar, with a numeric indicator of how many items were being represented by that tile). In all, users performed over 300 more window “focus” events (i.e., bringing the window to the top of the z-order for input) on the small display than they did on the large display.

For the large display, brightness of the display was mentioned as an issue by several users. Also, some users thought that they were forced to sit "too close" to the display, and they wanted to be able to back up and interact with it from a distance. In terms of windows design for the very large display, users mentioned the amount of navigation required and the problem of losing the cursor on the display were the two most onerous problems.

With regards to using dual or multiple monitors,this article provides some useful inputs on usability issues

In Tog’s article on Fitts’ Law, he describes how he experimented with “multiple desktops” (though at the time, it may have seemed more arbitrary than that). With a second monitor on top of the first, and a menu that users could “bypass” into the top monitor, it actually slowed the user down quite considerably: at first, the menu was missed quite often until the user slowed way down to get at the menu.

When using multiple monitors in a horizontal direction (a typical layout) the right edge of the left screen and the left edge of the right screen become very hard to hit. This especially becomes a problem with programs that are maximized. Consider the example of a typical scrollbar (normally on the right hand side) on a maximized application on one of the two monitors. On the left-side monitor, it becomes a hard target as the user has to directly aim and slow down to hit it. If on the right-side monitor, the scroll bar essentially becomes infinitely large and can be hit without any trouble at all.

Using multiple monitors also completely eradicates two of the five easiest locations to reach: two corners are no longer easily “reachable” – or perhaps reachable at all. This easy reachability of the corner is perhaps one reason that programs put the window control buttons in the top right corner; with another monitor on the right the corner becomes that much harder to hit. If there is a monitor above, then it becomes just that much harder.

As per this coding horror article It states that three monitors are optimal for users in general

As good as two monitors is, three monitors is even better. With three monitors, there's a "center" to focus on. And 50% more display area. While there's certainly a point of diminishing returns for additional monitors, I think three is the sweet spot. Even Edward Tufte, in the class I recently attended, explicitly mentioned multiple monitors

Lastly this paper by Microsoft research is a good resource and worth reading with regards to how perception is determined by screen size and screen area

Partitioning Digital Worlds: Focal and Peripheral Awareness in Multiple Monitor Use

Answer 2

One big advantage for software developers is that you can have your application running one one screen and your development environment running on the other. This means that there are hardly any issues when you have to switch your attention from one to the other. Having both things visible at a reasonable size at the same time makes it much easier and more efficient to test and debug the application. It's particularly noticeable when you are trying to debug an application that is constantly redrawing the screen.

While this is purely anecdotal, it has been backed up by several years of mine and my colleagues at different companies experience.

I would expect that this effect would benefit other users where there are two or more concurrent applications running.

Answer 3

Microsoft Research : 9..50%$ for copy & paste
Paper : 9%
Fujitsu-Siemens : 35%

The results aren't exactly blinding, but even the 9% make the cost/benefit ratio stellar.
(It would be interesting to see if the improvements descline after a while, though).

I couldn't find something on the limits, so here ar some personal observations:

2 is easy to set up, for most computers it's just "plug in a second one".
3 side by side seems to be a sweet spot, simply due to regarding required eye / head movement. Much of the benefit seems to be desktop real estate, but adding monitors scales much better than upsizing monitors. In addition, multiple monitors currently better afford arranging multiple windows via maximize on desktop. Mouse travel range works against number of monitors.

Answer 4

I recently started using more than one monitor, and I got couple of observations:

• Many people start using second, huge monitor (like ~24"), connecting it to notebook/netbook they've used before (so ~15"). That's giant difference, and much of initial excitement after buying second monitor has source here - there's just so much room for everything, compared to the usual, small display...
• But when you start using it, you find more and more benefits:
  • More room. For everything. If you work with several applications at once, you don't need to alt-tab between them, you just move your head - that saves lots of time
  • More information - you got more text on the webpage, more code in IDE, working with single application is easier as well. You don't have to hide windows you use not-so-rarely-but neither-all-the-time (so you don't have to look for them later) while maintaining same workspace as before
  • More general overview of what you do. If you design graphics, you see more without scrolling/looking at small miniature of your work. If you write a book or an article, you can (sometimes) rotate your monitor and see whole A4 page while not having to lean forward to read these small letters
  • This kind of matches others, but is worth mentioning - when doing anything, you focus on main monitor, and use second one for googleing or looking things up in documentation/reference. Such split is very natural and doesn't disturb workflow (it's like if you were reading a book and could either make notes at its end pages, which is meh, or in notepad on the side, which is yay ;)
  • Lots, lots of swag ;) (that's actually only half-joke - I find myself more comfortable while working, knowing I have professional workspace)

As for downsides - what I noticed - is that:

• I sit less healthy. I don't quite know what causes this, but maybe the fact that monitor doesn't fit the place where my laptop used to be, so I have to sit either closer to the monitor or further but less comfortable
• When you don't need the second monitor for some time, it's tempting to play some movie/match ("to just look at it from time to time"). It sometimes isn't problem, but may decrease focus on work
• Without some software utility, it gets some time to get used to. I use tool which creates second taskbar (on windows) on second monitor, and which introduces some shortcuts (like win+` to teleport mouse cursor between monitors) and utilities (like stopping cursor for 0.2 seconds before letting it go to other monitor)
• Windows has quite poor support for multiple monitors
• You need some adjustments to make for example colors match on both monitors, which may be tricky or even impossible

In overall, I'm very satisfied, but multiple monitors work differently for everyone. My girlfriend never turns on the second one, while my friend just uses one to work, and second one to watch funny sites. Oh well ;) You need to try it yourself anyway, but i think that for anyone above level of "email & word at work" it's almost a must-have.

Answer 5

It can greatly improve the productivity by preventing lots of window changing.

Below I give some examples:

• Being a software engineer, I need to compare code or documents once in a while, for comparing, put both items to be compared either on one monitor. This is almost impossible to do on one screen unless you make windows very small (resulting in using scroll bars).
• As a developer, it is nice to have the application to work at, on one screen and the running of that program on another monitor.
• Putting email and other notification programs on one monitor while 'working' on the other.
• When using cad/cam/graphic or any other program, run the application itself on one monitor, and the picture on another monitor.
• When watching a movie play it on one monitor and read websites/news on another monitor while being able to watch a movie.

These are just examples.

However, from a financial point of view: if you get only 2% more effective and your hour wage is like $50, a monitor of $200 returns in 200 hours, which is just 5 weeks of working.

Answer 6

List of usage scenarios I have encountered:

1. Work on one, watch the results on the other, random surfing/(news|stocks) ticker/TV/Game/Skype/Documentation lookup for the last

2. Program in linux, test browser compatibility in that other OS family that can run five major web browsers, look up API in the last

3. Code review setup with diff 1, diff 2, others. I find it a lot easier to compare stuff when they appear at the same time, so having twice the space to do that is just wonderful.

Answer 7

Adobe Systems has been putting significant effort into allowing its Creative Suite of products to be used with only one monitor. The effort has been touted in new feature press and interestingly their workspace optimization has been focussed on single monitor use. There are some examples cited below.

Anyone who has been accidentally tripped up CS UI's elaborate minimization buttons can see that its been a priority. I would question it - as dual or even triple monitors has proven to be the norm amongst professionals.

Dual monitors allow you to have an unimpaired view of the User's Experience. The only downside I see is that if the monitors are too large - there is a natural momentum to push the size envelope. Many UI professionals have one small monitor - 17 inches to keep them in what is increasingly a smaller space in terms of real estate, considering the growth of mobile and tablet devices.

• Illustrator workflow: http://help.adobe.com/en_US/illustrator/cs/using/WS714a382cdf7d304e7e07d0100196cbc5f-633aa.html

• Premier workflow: http://helpx.adobe.com/premiere-pro/using/workspaces.html

• Photoshop work flow: http://help.adobe.com/en_US/photoshop/cs/using/WSfd1234e1c4b69f30ea53e41001031ab64-750ca.html