Assumptions based on past experiences
This morning I was cycling to work and suddenly I heard a strange noise coming from the back of my bike. My initial thought was that my bag had fallen off so I stopped. The bag was still tied to the luggage carrier. I had made an assumption based on past experiences, checked the assumption and found out that it was wrong.
I tried to move the bike and heard something scrape against the mudguard. From past experiences I expected that some leaflet or piece of plastic was stuck between the wheel and the mudguard. Then I saw the cause: a nail was stuck in the tire.
I thought "there's no use trying to cycle further to work. When I pull out the nail the tire will immediately flatten". I parked the bike and took the bus home to pick up my car to get the bike home. Of course Murphy's Law made me miss the connecting bus to my house.
On the bus I checked the picture and then I started to wonder how deep that nail was stuck inside the tire. It didn't look that deep and my bike has tires that should prevent flat tubes. I got home, picked up tongs to remove the nail and drove back to the bike. I wanted to remove the nail so it wouldn't scratch me or the car. With the tongs I removed the nail and… nothing happened. No sound of a flattening tire and it stayed hard. The nail had left a little crack in the tire, that was it.
The thick tire did prevent the nail from punching the inner tube. I was used to thinner tires and my experiences were nothing but flat tires when something got stuck in them. I knew these tires would be thicker but the nail looked way bigger than the pushpin in their advertisements. That's why I didn't bother removing the nail before deciding to go home. I had made an assumption based on previous experiences but forgot to check it.