Which phenomenon describes the tendency for individuals to be more confident in their answers than is justified by the facts?

The overconfidence phenomenon refers to the tendency of individuals to overestimate their knowledge, abilities, or the accuracy of their answers above what is warranted by the evidence. This cognitive bias occurs when people have more confidence in their judgments than is supported by objective facts or statistics. Research in psychology has demonstrated that this overconfidence can impact decision-making processes, leading individuals to take unnecessary risks or fail to prepare adequately for challenges.

In contrast, the planning fallacy involves underestimating the time, costs, and risks of future actions while overestimating the benefits, which isn't primarily about confidence in knowledge or answers. The self-serving bias is about attributing successes to one’s own actions while blaming failures on external factors, focusing on self-evaluation rather than confidence in knowledge. Social facilitation describes the tendency for individuals to perform better on tasks in the presence of others, which does not relate to confidence in one's answers. Therefore, the overconfidence phenomenon is the most fitting description of the tendency to be more confident in one's answers than is justified by the facts.