If a user is entering text at a keyboard, then is forced to use their mouse for something (e.g. clicking a button in a modal dialog), what are the time and cognitive costs of that? Similarly, when users are not entering text, do they tend to interact in physical poses that are costly to switch out from?

Reading literature on GOMS analysis, I see a benchmark of a time cost around 0.4 seconds for switching, though I don't know where this figure comes from. It seems rather conservative, and doesn't seem to take into account the physical exertion and awkwardness I have experienced myself on switching.

Has any HCI or ergonomics research touched this topic?

  • 3
    FWIW, one should never have to use the mouse to navigate to a modal dialog button.
    – DA01
    Nov 30, 2012 at 23:00
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    The GOMS and KLM numbers are supposed to be used in a larger, multistep model. The 0.4 value alone isn't very helpful, but when you build a complete model with this method, the overall estimation is pretty good. Nov 30, 2012 at 23:55
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    Forget the costs in time and cognitive load. Focus on the costs in terms of irritating-ness... Unless an app uses the mouse as a replacement for a drawing tool (e.g. pencil) or similar, no application should require a mouse to function. Dec 1, 2012 at 10:25

1 Answer 1


Background: I have no background in UX, however am an avid computer gamer and power-user, so feel some of my opinions might be of use.

I personally play many games that "force" switches from mouse to keyboard in order to type, send commands, etc. I feel that it not only costs time, but reduces user immersion in the product, and actually ends up being a very frustrating experience if it happens too frequently.

Note that this also applys to the standard use of "left hand on keyboard, right on mouse" - so if you expect a user is using a mouse at a current time, its important to place all keys that might need to be used on the left side of the keyboard. ex. ctrl C, ctrl V, ctrl x, ctrl a, ctrl z, and many others - the only major office command that is not on the left hand is print, open, and re-do, and those are done rarely.

  • See this question for some details about the estimate of the homing time (H). Dec 2, 2012 at 19:58
  • Here are a few extra bits of information about H: (1) If you have a copy of The Psychology of Human Computer Interaction then look at Figure 7.4. It summarizes the data collected for estimating H. (2) Both KLM and GOMS are suitable for modeling human performance in well-learned tasks. They are not suitable for modeling the behavior of novice users or behavior for tasks that are not well-learned. (3) H did not address the possibility of the increased perceptual and cognitive processing demands of switching input devices. H = .4s estimates a manual action only. Dec 2, 2012 at 19:59
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    as a fun bit of added info - the left side of the keyboard can type long and tough words (ex. stewardesses, reverberated, and desegregated) - however using only the right side of the keyboard, the longest word you can type is Lollipop.
    – Nrgdallas
    Dec 3, 2012 at 20:33

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