Originally Posted by snowguy13
Thank you, snowguy. This is exactly it, and why I recommend that the habit of checking is adopted as early as possible. Learning in the simple scenarios makes it second nature in the complex ones, where you don't want to be distracted by unfamiliar effort.
And in reply to Omnamah, I would like to mention that human psychology can be a curious thing; magicians often use it to bewildering effect! We keep certain expectations in our heads without realiising it, and, when we are looking for something, we often gloss over possibilities that we think we already know, or try to match what we are looking for to a preconceived image in our subconscious, that may be distorted. Have you ever looked everywhere for something and not been able to find it, only to suddenly realise it is right in front of your eyes? How did you miss that!!! Well, the reason for that is as I have explained. So spotting a 2 where your subconscious wrongly "knows" there is a 3 is not as simple as you may think. Your eyes often see what they expect to see, and miss what they don't.