Take the 2-minute tour ×
User Experience Stack Exchange is a question and answer site for user experience researchers and experts. It's 100% free, no registration required.

I've noticed that most people when using a real or a virtual calculator, they hit the Clear button multiple times when clearing the screen (even though hitting it once is enough), so I started wondering: is there a flaw in the calculator's design that compels most people to do that?

What makes them trust the button less than the other buttons? Is there some sort of feedback mechanism that's missing? Even if it's just a habit, how does one end up developing it?

share|improve this question
121  
I usually do this with Ctrl-C (copy to clipboard) a lot. Sort of, I really, really, really want this copied. –  LarsTech Sep 21 '11 at 17:52
21  
@LarsTech I do that too, but usually because the program/hardware I am using at the time has 'skipped' copies before. Whether due to bugs, slowness, or rogue neutrinos, I could not say! –  Steven Noto Sep 21 '11 at 21:20
12  
It's an interesting habit, maybe it needs a name like Clearing Anxiety or Copy Anxiety :) –  Todd Sieling Sep 21 '11 at 21:33
7  
@LarsTech: IMO that behavior (I do it too) is caused by bad interface design, where hitting a key combo doesn't produce any visual feedback. On Mac OS X, for example, the menu corresponding to the key combo flashes briefly when you hit the key combo. –  houbysoft Sep 21 '11 at 22:52
25  
probably the same reason people hit the ESC in Vi/Vim multiple times to make really sure they are not in insert mode anymore. –  Jarrod Roberson Sep 22 '11 at 0:05
show 14 more comments

20 Answers

(Older) pocket calculators sometimes have several “cancel” buttons (C, CE, etc.) Typically, the CE button would only clear the last entry but not interrupt the current computation. For example, if you press 10 + 1 CE, you would see a 0, but the calculator still expects a second operand for the addition (i.e. it still has "10 +" in memory). Often, there would be no obvious indication of the current state of the calculator (i.e. is it reset and waiting for a new operation or in the middle of one?) If you want to start anew without having to remember which button is which or how a specific calculator works, you can simply press a couple of times on all cancel buttons and that's an habit many people kept from that time.

Windows calculator

share|improve this answer
16  
That's a pretty good explanation for those who have used such calculators, but many people (like me) haven't, yet they still have this habit. How can that happen? –  Mashhoor Sep 21 '11 at 20:54
106  
Yes, that CE / C button duality always drive me crazy, I newer know which one to push. So I push both and to be sure, push them several times :-) –  Tomas Sep 21 '11 at 21:58
12  
Many new calculators, particularly desktop 10-key calculators have this operating mode so I don't think it is really an issue of old calculators vs new calculators. –  Justin Ohms Sep 21 '11 at 22:01
72  
<ding>Ah, that's what the CE button is for...</ding> –  Lieven Keersmaekers Sep 22 '11 at 6:17
42  
The first calculators I used had a combination "CE/C" button; press it once to clear your last entry, press again to fully clear. I press C twice out of habit. –  KeithS Sep 22 '11 at 16:42
show 13 more comments

Other answerers have provided great logical reasons for how these habits could come about, but I think it is simpler than that (plus, how often are any of us logical?).

Calculators obviously have a state, since they do multi-step operations, but they don't clearly show their state. In many calculators, if you see a zero on the screen, you have no idea if the calculator is in the middle of an operation or not. So we press Reset a bunch to make sure.

Plus, many of us have gotten burned by starting a new calculation while the calculator was still in another mode, and gotten a totally unpredicted result. So we press reset a bunch to be sure.

Some calculators are better at this. For example the Win7 calc shows you prior operands. Some smartphone calcs show operands in vertical lines, and clear the screen when you press reset. Perhaps an even better enhancement would be to show the background screen in white if the calculator is truly reset, and colored if it's in the middle of something.

But there will always be the tendency to push the button a bunch of times, because better safe than sorry! ;)

share|improve this answer
143  
I pressed the upvote button several times. –  Patrick McElhaney Sep 21 '11 at 21:37
5  
+1 this is the root of the UX challenge –  Anson Kao Sep 22 '11 at 14:38
23  
@Patrick, odd or even number of times?? –  Tomas Sep 22 '11 at 14:46
4  
@tomas meta.ux.stackexchange.com/q/382/4508 –  Knu Sep 23 '11 at 0:40
6  
This is exactly why I hit Ctrl-C 5 times every time I try to copy but I only hit Ctrl-X once when I want to cut. –  Kevin Laity Jun 7 '12 at 14:58
show 3 more comments

On some old calculators, the clear button had double duty:

  • push once for clear-entry
  • push twice for clear-all

I think this meant that people tended to press clear a few times, to ensure that everything was cleared. It is possible that three clicks would clear the memory as well.

This is one of those habits that people acquired early on in the use of technology, which has continued despite the change in the technology.

And it is an interesting UX question, because the reality that clicking it multiple times has no additional effect does not change the perception. There are other cases of this, I am sure, but we actually just need to understand that this will happen.

Edit:

There is also the sense of clicking and clicking while I make the decision to move onto something else. It is not then based on habit, but just an attempt to reflect what is going on internally, that I need to clear my mind before I move on.

share|improve this answer
31  
Maybe if I press the door close button 50 more times this elevator will go faster... –  Ben Brocka Sep 21 '11 at 18:20
    
Schroedingers: But I've never used any calculator like that (that reqiores multiple clicks to clear), yet i still developed it. Same thing applies to everyone I've asked about this after reading your reply. Also some young people developed this, which is really strange. Ben: lol yea people do that as well, but maybe out of frustration? –  Mashhoor Sep 21 '11 at 19:45
4  
Oh I also forgot to add that I saw my young niece the calculator, and when she presses the Clear button, she presses it really hard then continue using the calculator. This mistrust is strange. –  Mashhoor Sep 21 '11 at 19:49
7  
+1 Yes, this. Not the fact that there are two clear buttons (C and CE), but that on many older calculators pressing C once cleared the current entry (CE), and pressing it twice cleared the entire calculation. I still have this muscle memory, and still press the C key twice, just because I don't want to have to think about it. –  Robert Harvey Sep 22 '11 at 2:32
2  
Wow, I've been using windows calculator for years and never noticed that "clear all" and "clear entry" were separate buttons. Note that the iPhone's built in calculator does exhibit this 2 presses to "clear all" behavior, so perhaps more of us have used this type of calculator than we realize? –  tobyodavies Sep 22 '11 at 2:33
show 3 more comments

Since there is no negative outcome to hitting the button multiple times, the question becomes really more of, "why wouldn't you hit it more than once?"

It would only take using a calculator with this behavior one time to create this behavior.

Think of it this way....

A person who has never used a calculator that works this way, one day uses a calculator that does. After some initial frustration, he learns that to clear he must hit the button twice.

He continues the rest of that day. Every time he hits the button only once his calculations are messed up (negative feedback) every time he hits it twice his calculation are correct (positive feedback)

The next day he uses a calculator that doesn't do this. However the behavior is already learned. But now whether he hits the button once or twice doesn't matter: both give positive feedback. Since both give positive feedback there is nothing to promote unlearning the behavior.

Now we continue on days or weeks later, he uses different calculators but doesn't really differentiate them. Hitting the button becomes like touch typing, a simple learned response.

When I type I don't think of the letters that I type or even how I move my fingers as I type. I just think of the words and brain an my fingers know how to make the letter appear on the screen. When I hit clear on a calculator I don't think "find the clear button, press the button x number of times" ... no I think "clear" and my fingers press clear (however many times they do.)

Now here is the really interesting bit. Say after awhile he does stop hitting the button twice. Ok well no problem on his normal calculator. However every time he picks up one of those other calculators, he's going to get negative feedback and the double tap behavior will again be reinforced.

Since he doesn't really differentiate these calculators when he picks them up, eventually his brain will determine that the cost in terms of effort of not hitting the button every time is greater than hitting the button unnecessarily. So... he just presses the button twice all the time.

share|improve this answer
    
"Since there is no negative outcome to hitting the button multiple times, the question becomes really more of, why wouldn't you hit it more than once." Just thinking to myself all the other things that might apply to, for example: Turning a door knob twice to make sure it's locked. With that sort of logic, why stop at two times, I mean maybe the second turn unlocked the door, right? –  blunders Sep 22 '11 at 15:49
    
@blunders Yep all sorts of things, but you might be thinking of it a bit wrong. I'm talking about an instance of positive or neutral feedback with no negative feedback. Actually your example of a door that unlocks when your turn it the second time is a good example of what I'm talking about. The behavior of the door is a great example of negative feedback. 1st time locks the door, 2nd time unlocks it.. therefore don't turn it a 2nd time if it want it locked. I do ~try~ to set my deadbolt twice but it doesn't turn the 2nd time, now if it gave me an electrical shock the 2nd time... –  Justin Ohms Sep 23 '11 at 0:32
    
My point is that some people are obsessive–compulsive, and no matter how much feedback they get, they'll almost insanely attempt to see if something different happens a second time around. This is not an interface malfunction, it's a user malfunction. –  blunders Sep 23 '11 at 1:17
2  
@JustinOhms You're very correct! The way this happened to me (and I would guess, many) is that one of my first pocket calculators had really crappy buttons and would often need a firm, long press to ensure it worked. The failure of a number or operation key to work produced immediate and obvious feed back, but the clear key failing is just as you described in your answer. +1 –  William Grobman Sep 24 '11 at 15:50
1  
add comment

I'm going to departure a bit from the current line of thought. Back in the typewritter days, I remember seeing my dad's accountant typing really fast on the machine. Whenever he paused for any reason, he kept pushing the "shift" button several times in a row.

He knew pressing that key didn't do anything, and that was exactly the reason he pushed that key... it didn't do anything but kept his fingers busy, or gave the impression that he was busy, or simply because it helped him to keep that rhythm, who knows...

My claim is that some people will press the CE several times just because they know it won't do anything, and that's it.

share|improve this answer
9  
On my typewriter, shift did do something, namely remove the caps-lock if it was activated. So it could be the same issue: to make sure the typewriter is in "normal" mode, a shift "is always good". Same as hitting Esc before any operation in vim, instead of looking at the (rather poor) mode feedback. –  giraff Sep 23 '11 at 7:00
1  
This is an excellent observation, I sometimes also hit on the table or something when I'm concentrated at something and don't want to lose the line of thought. –  Trufa Sep 23 '11 at 21:01
    
giraff, I understand the functional use of the shift, but in my observation, the accountant (in fact I've seen the same behavior in other people as well) would type shift in rapid continuous succession for about 2 or 3 seconds while he was checking what he had just typed. It almost seemed like he didn't want "to turn the engine off" –  Padu Merloti Sep 23 '11 at 23:16
2  
Similar to Starcraft players who are pressing things just to keep fingers occupied and blood flowing etc: gaming.stackexchange.com/questions/21647/… –  Kris C Sep 25 '11 at 23:30
    
I thought I was the only one. I frequently get to see the "Do you want to turn on Sticky Keys?" dialog because of this habit. –  Doug Chase Nov 9 '11 at 0:41
show 1 more comment

It is low-cost fidgety action (on user's part) combined with a device that offers low levels of feedback for that action. Such a combination makes you want to repeat that affirmative action.

I find myself using ctrl-c multiple times for the same piece of text. I would do that much less often if MS Word's clipboard manager were open or I had a sys-tray app that blinks every time I use ctrl-c.

As another example, I face conversations where I am disinterested and the other too enthusiastic. He may repeat certain phrases ("job security", "future", "career") to compensate for my disinterestedness. But if I repeat that phrase in front of him, I find that he moves on.

Test for my hypothesis: would a user repeatedly press that button if it gave a satisfying click, or the screen blinked once?

share|improve this answer
5  
+1 Good point view. However these "low-cost fidgety action" have a name: compulsions, and they're not necessarily symptom of a disorder. And to answer your last question, sometimes yes, sometimes no. I've seen a friend of mine martyring my poor Casio even if it blinked after clicking the clear button... And I've seen myself clicking Ctrl-X more than once when cutting files in MS Windows, where they become 'translucent' (so there's a feedback) –  gd1 Sep 22 '11 at 13:41
add comment

Slow feedback can cause this. It makes the user feel like the button is broken and needs to be pressed again or harder, which would work in the real world.

Did it work? Did it really work? Really?

...also, just general frustration. We're used to some button-presses being idempotent (as with an elevator): once pressed, additional presses are a no-op, so if people are bored and waiting (think: crosswalk buttons), or annoyed with the interface, they may hit it a bunch of times.

Repeated presses may also be used for emphasis--"Clear, dammit!"--or for efficacy--in conversation, we're used to having to work very hard to 'erase' a previous statement.

Finally, a button press takes less time than it takes for the user's mind to switch tasks, so while the mind is switching, just keep pressing 'clear' to keep the hands busy. Otherwise you're gaping at a blank screen and forget what you were doing.

share|improve this answer
add comment

These people, I have to admit myself included, have had experiences before with calculators that if they hit clear or 'C', and do a math expression, the result is incorrect. So in their mind, they hit the clear button several times to "totally clear" the contents before proceeding.

Have you also noticed that they will hit the 'C' and 'CE' buttons over and over again, not just 'C'? They are not sure which one does which, so they just slam on both of them until they feel satisfied.

share|improve this answer
2  
Agreed, sometimes I've clicked them in the past just to make sure I've cleared the memory contents. –  wonea Sep 22 '11 at 13:43
add comment

I'm going to answer this question with another question: why do people press the elevator button multiple times, some even if a light indicator turns on immediately after the first time? You see this often with old people. I think the answer is psychological.

Most people by now are pretty accustomed to the way electronics and digital circuitry works: things are usually either on or off. Pressing the button elevator multiple times won't make it come faster, resetting the calculated multiple times won't make it reset "harder". Still, this model of interaction with hardware relies on an assumptions that things work as expected. I believe most of us still have a lot of analog habits, though, and in the analog world you sometimes have to apply yourself a bit more to get stuff to work. We know that sometimes you have to jiggle a key so the lock works and sometimes you have to hit the fan so it stops making a noise.

It doesn't necessarily mean that things have to malfunction for us to give them an "analog" treatment. Sometimes we perceive things as just a bit more complicated than we'd like them to be, and in the trade-off between not being sure whether the elevator's button has registered the signal (which makes us feel worried about waiting like idiots for something that's not coming) and between just one more push of a button, the latter is often the more cost-effective choice.

So, to summarize, even digital things sometimes work in unexpected ways (due to malfunction or hidden complexity) and when faced with this uncertainty many people fall back to their analog habits of giving HW an extra nudge to make sure it knows what they want from it.

share|improve this answer
add comment

I think most of the answers given here are just post-hoc justifications. There is no actual reason why you should press the clear button 4-5 times.

It's simply a physiological (not pathological) compulsion.

We do a lot of compulsive actions every day, every time, even the people not affected by any mental disorder. Just reflect upon yourself and you'll find how many rituals you perform. And it's typical of the compulsive behavior itself finding excuses ("It was necessary in old calculators", "I just want to make sure", etc...) which are plain bullshit... :)

Just to clarify... Compulsions are full of logic, from their own point of view, but this 'logic' doesn't resist a bit of reasoning. An example? Telling that pressing the clear button n times was necessary in old calculators (so you keep on doing in this new device even if unnecessary), doesn't resist this simple objection: did old devices really needed to be 'cleared' up to 5 times? :D
It's just like triple/quadruple/n-ple checking the gas knob. "I have to do it because someone didn't and blew up the house". That's fine. But isn't it 100% safe to check it once? Checking it 5 times won't make it 500% safe... "But the first time I could have checked it the wrong way!" ... Which way it's wrong?
And soooo on... :)

So it's just unnecessary. Once you realize it and you stop finding excuses, you have some possibility to discard the compulsion.

So: no logic reason, just a widespread compulsive behavior, like biting one's nails.

share|improve this answer
9  
This might be true for many things but I definitely hit the cancel button on the calculator several times because in the past I got wrong results because one of the buttons doesn't clear everything and I never know which one. Some things do have a logical explanation ;-) –  Omar Kohl Sep 21 '11 at 22:23
3  
I'm sorry to tell you -- and please note that I'm NOT telling you that you have a problem -- but this is exactly how a compulsion works. It 'finds' reasons to keep some behavior living even after it's not needed / not useful / not logical anymore. And compulsions 'love' finding logical explanations. –  gd1 Sep 21 '11 at 22:24
3  
And if just knowing something made stopping a habit possible, we'd live in a very different world. Sadly, abstract knowledge doesn't map to the patterns of the nervous system all that well. –  Todd Sieling Sep 21 '11 at 22:25
7  
@gd1 You are essentially making an assertion that this behavior is "not needed/ not useful / not logical" which quite obviously is a false statement simply by the evidence of the fact that there have been numerous people on this very page that clearly have "useful" and "logical" reasons for doing this very thing (even when the particular device in question does not require it) –  Justin Ohms Sep 21 '11 at 22:35
3  
I don't have a compulsion, but I get annoyed if I have keyed in a complex calculation and it is messed up because I didn't double click to clear entry and clear all. @JustinOhms's answer has it right for me. –  Rory Alsop Sep 22 '11 at 8:27
show 6 more comments

Note that on simple calculators, both C and CE shows a zero after hitting it. For users who do not frequently use the calculator, it is counter-intuitive to "manually" recall what is the previous state. It is also often unclear which one is the previous state so these users end up having to start all over again. So pressing C and CE is both ensuring that the calculator really is starting from zero and for the user to take a deep sigh!

For users who frequently use calculators and are familiar with the C and CE buttons, or who knows the feature really well, it is more likely that they will only hit the button once. I would not imagine them hittin the CE more than once, but if they do it on the C button, they are probably not thinking of clearing the calculator but rather a fidgety action while they are deep in thought thinking about what to key in for the next calculation.

share|improve this answer
add comment

It's a deep instinct that something is more assuredly "done" if the act of doing it is repeated. Why does a dog make little circles before it lays down? Why do people hit the crosswalk button over and over and over when deep down they know that it won't make the light change any faster?

We do receive positive feedback in many such cases. For example the more times I hammer a nail the more sure I can be that it's driven all the way in. The more times I chew a bite of food the less likely I am to choke on it and the easier my digestion will be. There are countless other examples of 'assurance of completion by repetition'. People are simply doing something that comes quite naturally to them: generalizing their experiences and applying them to new experiences. And as previous posters have noted, there is no negative feedback; there is no reason to not press the button repeatedly.

In the case of people who push the crosswalk button again and again, I usually attempt to be the negative feedback by poking fun at the irrational behavior. Your calculator, if you so chose, could do the same sort of thing. A single click would simply silently clear. A second click would produce a popup stating, "Yes. We have officially cleared the calculator now. One click will suffice. Thank you." People will be annoyed at the popup which will require another click to get rid of, and they will soon learn to click only once. Either that or they'll learn to use a less snarky calculator. ;-)

share|improve this answer
1  
I would smash that snarky calculator into a thousand pieces, for the record. –  Graham Sep 26 '11 at 15:33
add comment

Though mono-causal thinking is often for questions like this and makes for the good reading, there are multiple reasons why people do this and the primary reason may vary from person to person.

The user is probably aware (judging from the feedback here at least) that the action is not necessary or useful, but they feel compelled to do so regardless due to a number of physiological or psychological compulsions such as brought on by a combination of the following:

Stress, Nervousness, Habit, and the desire to fidget; not helped by stimulants (caffeine mainly I hope)

Also consider: When people press clear, it is just before they type in another calculation so they are in thought and thus not paying particular attention to what their fingers are doing, exacerbating these effects.

share|improve this answer
    
It's quite possible that there are multiple reasons for this behavior but the ones you mention do not seem to explain anything at all. They would just as well apply to pressing any other key or manipulating any other object, yet the question is why do people (seem to) do it more often in this particular situation? –  Gaël Laurans Feb 6 at 18:12
add comment

Some of the credit-card sized, solar-powered calculators (without a battery backup), which were all the rage in the early 1990s, didn't always reset to the initial state completely when under a low-light condition, after pushing the C (clear all) button, and thus would behave unpredictably after such "incomplete reset" - I think some of the registers were not cleared due to very low power provided by the small solar panel. For this reason, it was customary to press the button multiple times - which prevented the problem.

Also, some models of the calculators had the buttons combined into one: CE/C - first push would erase the last entry, second would reset to initial state.

here.

share|improve this answer
    
The C/CE issue is already mentioned in this answer –  ChrisF Mar 23 '12 at 9:37
    
@ChrisF: True. However, I haven't seen the physical reset issue mentioned in any other answer. –  Piskvor Mar 23 '12 at 9:39
1  
My understanding is that while calculators are made of of latches which are each supposed to be either "high" or "low", reducing the voltage on a latch just the "right" amount before reapplying power may leave it in an intermediate state. Latches which are in such states may draw more current than latches which are cleanly high and low, and this current draw may "drag down" the supply voltage below the level required for reliable operation. Pushing reset once will kick any latches that were not cleanly high or low, and ... –  supercat Dec 3 '13 at 23:05
1  
...will allow the supply voltage to rebound within a half-second or so, but the fact that the voltage was low when the button was pushed may cause the calculator to have not reset cleanly. A second push after the voltage has rebounded would resolve things. Given that many people have sometimes used calculators with a CE/C button, pushing twice as a matter of habit is easily explainable as either occasionally-necessary behavior, or a consequence of seeing others do it. –  supercat Dec 3 '13 at 23:08
add comment

There are probably a few explanations.

  1. It is an action that is easy to perform and with little consequences.
  2. Many calculators do not give sufficient feedback. Imagine if when the data was cleared you got a mechanical thunk. Would you feel the need to do that again?
  3. In a similar vein, calculator keys are easily stuck. Therefore it could be a learned behaviour based on past experience.
  4. The habit can be learned through exposure to other's habits (This might explain why some people do it but not why it originated)

And 2 reasons that are a bit more speculative:

  1. It can sometimes be performed at a moment of anxiety. The 'oh damn' that's not right moment.
  2. In some cases it could be a form of fidgeting. A physical movement to project action (or intent) to others. A bit like a routine that signified your engagement with the calculator but giving you time to think about what you are doing (like some people use 'um' in conversations). Signalling that these users are thinking about what they need to do.
share|improve this answer
add comment

My guess is most people have experienced accidentally re-using the result of the last calculation in the next calculation they're trying to make.

Once I was adding a sequence of numbers and got in the habit of hitting the plus key after each number, THEN looking at the next number. I got distracted, moved on to a new calculation and came back and started entering a new, unrelated number only to discover it was added in to the previous result by mistake.

This got me in the habit of pressing the C button frequently on in-fix calculators.

For what it's worth, I grew up with Hewlett-Packard RPN calculators, and when I use them, I virtually never clear the previous register contents since it's much less likely you'll accidentally use a previous calculation with post fix calculations.

So... I'm going for the "I just want to return the calculator to a known state" explanation.

share|improve this answer
add comment

The repetitive punching of the clear button is really caused by the user not knowing the difference between CE and C. CE clears the current entry, but C clears the entire operation. When most people punch the clear button multiple times, it means they want to clear the entire operation. But because CE and C both give the same feedback when they hit it, there's no way of knowing if the entire operation is cleared for someone who isn't sure what the difference between the two buttons are. So by pressing it multiple times, the user feels that the entire operation gets cleared, not just the current entry. Here's a great article that offers an innovative solution to the current calculator interface: http://uxmovement.com/thinking/why-calculators-need-a-better-user-interface/

share|improve this answer
add comment

Most people who do so (I am definitely not one of them, but have seen people doing it), would have had bad experiences at some point in time, for example, the previous numbers being used for the next calculation because the C key didn't clear it up. I've also seen people pressing Ctrl+C or Ctrl+S multiple times, and people even repeatedly right clicking their desktops and pressing refresh (Windows only).

There could be multiple reasons for these habitual actions (most people wouldn't think or even wouldn't know that they do this):

  • They realized that these actions didn't work when done only once, there was a possibility of error, and want to be sure.
  • These actions do not provide a visual cue or feedback. The calculator screen shows zero even when you press 5 followed by +, or press C. Ctrl+C doesn't show (except in apps like MS Office) that you've copied something. Ctrl+X or Ctrl+V, for instance, show that something has been cut or copied, and the user would repeat these actions only when they know that it didn't work the first time.
  • Actions like these are harmless, and make the same changes to the system when done repeatedly. That is also why you'd Ctrl+C thrice but Ctrl+V only once.
  • People want to pause to think at times, and their otherwise fast actions do not give them enough time. These key combinations provide them, of course subconscious, gaps to think.
share|improve this answer
add comment

I think the simplest explanation and one in which I have no evidence, is our need to be as thorough as possible. We want to make sure something has been done properly. Not everyone will have this compulsion.

A similar example is if I lock my car using the remote fob, I still feel the need to double check the door handles to make sure its locked. I may even walk away from my car only to return and check again! I know, crazy.

share|improve this answer
add comment

There is a simple reason:

Pressing Ctrl+C or Ctrl+S is a double-key combination, so it has higher probability of mistyping. If I am typing at my fastest rate, then this is part of a streaming sequences of stuff I am doing. Pressing it more than once greatly reduces the probability of error, whereas if I had to stop and intentionally considered each Ctrl+C, this dramatically reduces my typing efficiency.

In other words, while a single, conscious single press is enough. In practice, a single press is not sufficient in practice to statistically produce the low error rate and high efficiency that results from inserting a few extra double presses.

share|improve this answer
add comment

protected by JonW Nov 8 '13 at 11:09

Thank you for your interest in this question. Because it has attracted low-quality answers, posting an answer now requires 10 reputation on this site.

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.