In below unremarkable picture, the bottom line is obviously longer than the top.

That's what we all see, and we tend to believe what we see. However, the lines are identical in length.

So, now you know the lines are equally in length, but you still see the bottom line as longer. You cannot decide to see the lines as equal although you know they are. This is a simple example of how we must learn to mistrust impressions, in this case, lines when fins are attached to them.

As leaders it's important to recognize that not all illusions are visual, there are lots of cognitive ones that can fool us each day unless we pay attention and distinguish between impressions and beliefs.  

Adopted from winner of the Nobel Prize in Economics, Daniel Kahneman's awesome book, 'Thinking Fast and Slow'.
