Answer:
Stan is using a person-who reasoning to justify his junk food eating behavior.
Step-by-step explanation:
In psychology, the definition of reasoning is the mental process through which people find reasons for beliefs, ideas, actions, conclusions, or feelings. In Stan's case, he is using what is called person-who reasoning. In that type of reasoning, the individual questions well-established research findings because he/she knows of one instance, one person, who violates those findings. Stan is doing precisely that when he justifies his behavior by using his grandfather as a reason. He is failing to see that he is focusing on the exception, not on the rule.