If we want a user to perform a certain action, we make it easiest for them to select that option compared to any other available option.
For example, think of a pop-up ad, "Do you want to download/install/sign up?"
You want the OK button to be more prominent to encourage users to click it. Some designers would make it larger than the other button. Others rely on eye travel, putting it above or to a certain side of the other.
Please note, I am in the US, where eye travel is left to right. Therefore, if you put the button to the left, it will be the first one that a user sees when scanning the available options, making them more likely to agree without noticing the Cancel button. If you were to put the Cancel button first, then users are more likely to realize that it is an available option and opt out.
(I understand there are many reasons to put the OK/Cancel buttons on the left or right, many of which are discussed in OK/Cancel on left/right?. For the purpose of this question, I am referring to reading left-to-right, so I like the point that Cancel/OK is like asking "No or Yes". However, since I am asking about eye movement, Why 'Ok' Buttons in Dialog Boxes Work Best on the Right makes an excellent point that users might read both options before deciding.)
Now, my question is with mobile devices. An overwhelming majority of people are right-handed (I found figures of 70-90%). Assuming that they would use touch screens with their right hand more often, it would be easiest to click the button closest to your right hand so you don't have to reach your finger or move your arm as far.
But this directly contradicts my point about eye travel. Is there a best order to put OK/Cancel buttons when designing for mobile? What about in countries that read right-to-left?