It is often assumed that reasoning occurs on an individual basis. However, humans reason in groups, rationality is a collective project.
“Collectively, a group can know more and reason better than an individual, and thus human beings with the social and intellectual skills to pool knowledge had a survival advantage over those who didn’t”
Humans can be pressured to change their mind via group pressure even on simple subjective judgments:
“The twist, however, was that the subjects weren’t alone. There were also five to seven other participants who were actually working for Asch. And every so often, they would all give the same wrong answer. These were called the “critical trials.” The results were remarkable: on critical trials, the participants gave the wrong answer 37 percent of the time. Given the choice between what their eyes were telling them and what the group was telling them, they went with the group. “I felt conspicuous, going out on a limb, and subjecting myself to criticism that my perceptions, faculties were not as acute as they might be,” said one of the subjects in a post-experiment interview.”