Can Your Common Sense Survive These 8 Questions?

Questions like these come from research into what psychologists call reflective thinking — the gap between the answer that arrives instantly and the answer you get by checking. The bat-and-ball question in particular is famous for catching highly educated people.

The pattern is always the same: the question hands you an obvious number or an obvious assumption, and the obvious one is wrong. The only reliable defence is to reread the sentence before you commit.