Why does mobile phone auto correct fail?

Question

You know what happens when you type anything on a mobile device, it corrects your spelling to something you didn't want. But you don't realize it until you've sent the message, and then it's too late, the damage is done. Hopefully everyone gets a good laugh, but it isn't very useful.

• On Twitter the hash-tag #dyac generates a lot of posts from frustrated users
• The web site http://www.damnyouautocorrect.com/ has almost 6000 screenshots of auto correct not working (one of them visible in the image below)

Microsoft Word 2010 spelling work very well. OneNote Web App and Google Docs also spells very well, to my knowledge. Is it a great idea that failed on implementation? Is the local memory of the phone too small? I don’t know, but I do want to know:

Why does mobile phone auto correct fail?

Answer 1

Typing on the phone is much more difficult than on the keyboard, so people make more mistakes and the phone autocorrect has to work much harder.

1. Keyboard mistakes come from actual grammar mistakes and from typos, which are usually caused by typing an adjacent key by mistake - in most cases the wrong key is the one immediately to the right or to the left of the correct key. So this is relatively easy to recognize and to correct. Whereas on the phone, half the keyboard is adjacent to each other, and instead of two probable keys you have about nine if not more.
2. On the keyboard it's extremely unlikely that you press a key when you didn't intend to press any keys at all - the typos come from intending to press key A and pressing key B instead. Whereas on the touch screen, we accidentally touch the screen as we move our fingers across it, and a key is pressed. Trying to figure out what the user meant is bound to fail, because he didn't mean to press anything. That's more noise to the system.
3. PC autocorrect is usually just that - autocorrect, while phone autocorrect acts very often as autocomplete, suggesting words to us. Since we're eager to get the typing over with, we don't pay much attention and often we accept its suggestions without looking. On some keyboards you just need to hit Space to accept, so in many cases people aren't even aware that a suggestion had been made to them and they accepted.
4. The small size of the mobile screen, made even smaller by the keyboard taking up half its size, causes the top part of the text to float out of view by the time we're done typing. So we just don't catch many of the mistakes we'd notice if this were a larger screen and the entire message would fit.
5. Typing on the phone is difficult, so we concentrate on the keyboard, and we don't notice what's happening on the screen. The input process draws our attention away from the output. That's another reason why many mistakes go unnoticed.
6. On the phone, there are mechanisms at work which don't exist on the keyboard, and they interfere with our typing. E.g. the iPhone increases the target size of keys it thinks you're likely to hit next. This might make it easier for novice users who type slowly, but it makes it difficult for us to become experts, since the system is unpredictable, and tapping the same place might yield different results in different contexts. This adds more noise to the system.

If I had to guess, I'd say that Blackberry, or full QWERTY keyboard mobiles in general, have much less autocorrect failures than touch screen devices.

Answer 2

To make "Autocorrect" work, there are several key components play here.

1. The prediction algorithms, obviously.
2. The dictionaries being used
3. The perceived necessity vs. "feature-pushing"
4. Why iPhone users "suffer" more ?

Mr. Vitaly's answer is quite enlightening. I just want to add my 2-cents.

The prediction algorithms: Of course, they are different for different vendors, and different keyboard software. But, they often try to be quick & smart rather than effective & non-obtrusive. They usually prefer more-frequent words rather than right word for the context, because context analysis is quite-challenging & CPU-intensive than suggest from a frequency table.

The dictionaries, being used, are quite standard. They mostly fail to recognize local, slang, urban words even they are wildly popular. Text messages (sms), as in the OP's screenshot, are far more personal, hence informal, than formal. Emails, on the other hand, is more formal than informal. Keyboard software definitely don't (or can't) differentiate that usage.

"feature-pushing"? Do someone want "autocorrect"? Yes, maybe. Do they want it "pushed ON" by default? Definitely NOT.

from the receiver's side, it is way much understandable a typo than a "correctly spelled" wrong word. e.g. "you smsrt asses" is far more understandable that "you smart assets".

Why is that "Auto-correct" is turned on by default? Does the UX designer understand the true cost of sending "correct" absurd message to someone's manager vs. "typo-ed" meaningful message?

Why a feature almost absent to PCs is trying to become so smart in a much-more sensitive device?

for iPhone users, I think, it is more deadly due to the absence of 3rd-party keyboards for iphones, due to Apple's restrictions, up until recently.