> Otherwise known as the standard normal distribution. It crops up a lot when talking about traits in a population, such as intelligence. The reason for this is

> Otherwise known as the standard normal distribution. It crops up a lot when talking about traits in a population, such as intelligence. The reason for this is well understood (see central limit theorem) and won’t concern us here. No, the reason IQ follows a bell curve is that IQ is defined as following a bell curve. Results are adjusted to make a bell curve.