The John Henry effect is named after a man called John Henry who was a legendary steel driver that competed against a steam-powered hammer to tunnel through a mountain in the 1800s. The story says that John Henry won the competition but died shortly after due to exhaustion.
Now, the John Henry effect refers to the idea that people can work harder and perform better when they know they are being observed or compared to others. This can happen in many different situations, like in school when students do better on tests if they know their parents or teachers are watching or at work when employees might work harder if their boss is watching.
The idea is that the pressure of being watched or compared to others can make people want to do their best. It's like a game or a competition, and people want to do well in those situations. This effect can be positive if it motivates people to do their best and improve, but it can also be negative if it causes stress or anxiety.
Like John Henry, people might push themselves too hard to win or perform well, and that can have negative consequences for their health or wellbeing. But, generally, the John Henry effect is a good thing that can help people do their best and reach their goals.