After a semester of psychology, one of the concepts that I will remember clearly is inattentional blindness. Inattentional blindness is defined as failing to notice something that is in plain sight due to being focused on something else. We have all experienced it at one point or another, however we never seem to notice it. When you look at it, inattentional blindness can be both a blessing and a curse. It's bad in that we might miss something important. An example of this is failing to notice a speeding car heading towards you as you are crossing because you are texting someone. However it isn't all bad, If we actively noticed all of our surroundings, we would be overwhelmed with information to the point that it would impair our ability to function properly. We need to zone out some stuff in order to focus on what's important, noticing the color of the bike you just passed can be the last of your worries.
So remember, next time you see a friend and wave at them from afar, yet they don't notice you, they are most likely exhibiting inattentional blindness.
Finally here is a video that illustrates this phenomenon in action:
How many changes did you spot?