The Goldilocks principle states that when some quality of the items in a sufficiently large given sample can be arranged on a scale ranging from one extreme to another extreme (for example from extremely cold to extremely hot), some items will fall in a moderate range between these extremes. When the effects of the principle are observed, it is known as the Goldilocks effect.
The name of the Goldilocks principle is derived from a children's story, The Three Bears, in which a little girl named Goldilocks finds a house owned by three bears. Each bear has its own preference of food and beds. After testing all three examples of both items, Goldilocks determines that one of them is always too much in one extreme (too hot or too large), one is too much in the opposite extreme (too cold or too small), and one is "just right".[1]
The Goldilocks principle is not a hard law, but examples in which it applies are found across many disciplines, particularly developmental psychology, biology,[2] economics and engineering.
https://en.wikipedia.org/wiki/Goldilocks_principle