It would come as no surprise to me if 1 in 10 iPhone users had broken their iPhones by slamming them against walls after it’s auto-correct dictionary kept suggesting the wrong words. Whether that is the case or not, who knows, however with thanks to Ars Technica the way for the iPhone to actually learn the way you type is via one application, Safari (on your iPhone).
To do so, you’ll need to type into the ” google search” in Safari and ensure you correct the spelling of any words that the iPhone recommends to you. By doing so, you overwrite the iPhone’s auto-correct dictionary (located at /private/var/mobile/Library/Keyboard/dynamic-text.dat).
To summarize, not every application will “learn” words based on what you type – currently (according to Ars Technica) only Safari will.