Visual Search Problem
Visual perception accomplished in our brains is a fascinating process. There are many interesting features that one comes across. One of them is the visual search problem - the objective is to identify an odd image amidst a group of distractor images in the shortest time. Put differently, certain kind of symbols are more easily recognizable when placed amidst a group of similar looking symbols whilst others are not. For instance - symbol 'V' amidst symbol '^'s (inverted V) are very easy to spot. On the other hand, symbol 'S's are much more difficult to spot amidst symbol '2' (mirrored S). I could personally relate to this phenomenon while solving a 3x3 Sudoku in the shortest possible time.