The catfish effect is the effect that a strong competitor has in causing the weak to better themselves.[1]
In Norway, live sardines are a few times more expensive than frozen ones. It was said that only one ship could bring live Sardine home, and the ship master kept his method a secret. When he later died, people found that there was one catfish in the container. The catfish keeps swimming and the sardine becomes very active to avoid direct contact with this Catfish.
In human resource management, this is a method used to motivate a team so that each member feels a strong competition, thus keeping up the competitiveness of the whole team.
The exact origin is unknown. There are very few discussions of this effect in the English literature, but it is widely cited and discussed in the Chinese literature such as library research.[2]