Final answer:
The term for using similarity to a prototype instead of probability is the representativeness heuristic, which often leads to judgments based on superficial traits rather than actual probabilities. So, the correct answer is the representativeness heuristic.
Step-by-step explanation:
When people use similarity to a prototypical example rather than probability, it is known as the representativeness heuristic. This cognitive bias occurs when individuals presume that something or someone is typical of its category because it looks similar to a prototype they have in their mind, despite statistical evidence to the contrary. A classic example is when individuals assume a well-dressed individual is more likely to be a successful business person, even without any factual information about the person's career.