How many holes does this t-shirt have? Only one in seven people gets the answer right.

The question is simple: how many holes are there in this t-shirt?
The choices offered are clear: 2, 4, 6 or 8. 

Many people instinctively answer without thinking too much. Others take a few seconds, recount mentally, hesitate… and change their minds. The result: only one person in seven gets the answer right the first time. It just goes to show that even everyday objects can play tricks on us.