Answer: Representativeness heuristic.
Step-by-step explanation:
Representativeness Heuristic is a mental shortcut that leads people to make assumtions based on a generic example, usually a mental prototype based on stereotypes.
The gambler's fallacy is a type of Representativeness Heuristic that leads people to believe that if something occurs more often than usual during a certain time, it will be less often in the future, and vice versa.
When this observation is made over surely random events, this belief is mistaken, such is the case with gambling players.