“What happens when people who share a belief get together to discuss it? Psychologists know the answer to that and it’s not pretty. They call it group polarisation.
It seems reasonable to think that when like-minded people get together to discuss a proposed hazardous waste site, or the breast implants they believe are making them sick, or some other risk, their views will tend to coalesce around the average within the group. But they don’t. Decades of research has proved that groups usually come to conclusions that are more extreme than the average view of the individuals who make up the group. When opponents of a hazardous waste site gather to talk about it, they will become convinced the site is more dangerous than originally believed. When a woman who believes breast implants are a threat gets together with women who feel the same way, she and all the women in the meeting are likely to leave believing they had previously underestimated the danger. The dynamic is always the same.”
Hence the value of diverse teams, presumably.