I'm pretty confident to assume you haven't, or at least most of you haven't anyway ....I certainly never had.
When the lid is removed, those fleas for the rest of their lives will never jump higher than the level of the lid. And what is truly amazing, is the offspring of those fleas will never jump higher either subhanAllah.
You can see the experiment for yourself in this short one minute video [click here].
When I saw this, I immediately thought about the conditioning of my own upbringing; how my parents have influenced my behaviour and then I thought about how I influence my children in theirs.