What psychological principle suggests that people are influenced by others' decisions or actions?

The principle that people are influenced by others' decisions or actions is known as consensus. This concept is grounded in social proof, where individuals look to the behaviors and decisions of others as a guide for their own actions, especially in ambiguous situations. When people see that a majority is making a particular choice or holding a certain opinion, they are more likely to conform to that behavior, believing that it is the right or acceptable thing to do.

This principle can be particularly powerful in shaping perceptions and behaviors in various contexts, such as marketing, group dynamics, and social interactions. For instance, if a person observes a large group positively responding to a product or idea, they are more likely to follow suit, thinking that the popularity of that choice indicates its value.

In contrast, the other options relate to different psychological principles that influence behavior. Authority pertains to the influence of a recognized leader or expert, reciprocity deals with the mutual exchange of favors or concessions, and scarcity focuses on the perceived value that comes from limited availability. These concepts also play significant roles in human behavior, but they do not specifically highlight the impact of group decisions or actions like the consensus principle does.