"If reasoning evolved so we can argue with others, then we should be biased in our search for arguments [since] In a discussion, I have little use for arguments that support your point of view or that rebut mine. Accordingly, reasoning should display a confirmation bias: it should be more likely to find arguments that support our point of view or rebut those that we oppose. Short (but emphatic) answer: it does, and very much so. The confirmation bias is one of the most robust and prevalent biases in reasoning. This is a very puzzling trait of reasoning if reasoning['s purpose was]... bettering our beliefs—especially as the confirmation bias is responsible for all sorts of mischief….[but] Interestingly, the confirmation bias needs not be a drag on a group’s ability to argue. To the extent that it is mostly the production, and not the evaluation of arguments that is biased—and that seems to be the case—then a group of people arguing should still be able to settle on the best answer, despite the confirmation bias…As a matter of fact, the confirmation bias can then even be considered a form of division of cognitive labor: instead of all group members having to laboriously go through the pros and cons of each option, if each member is biased towards one option, she will find the pros of that options, and the cons of the others—which is much easier—and the others will do their own bit."Why we need other people to bounce stuff off of: (whether we realize it or not)
"When people reason alone, there will often be nothing to hold their confirmation bias in check. This might lead to distortions of their beliefs. As mentioned above, this is very much the case. When people reason alone, they are prone to all sorts of biases. For instance, because they only find arguments supporting what they already believe in, they will tend to become even more persuaded that they are right or will develop stronger, more polarized attitudes."