Philosophers like to believe that reasoning helps us arrive at truth, ridding us of false beliefs and helping us make better decisions; that reasoning is the best way of being rational. Psychologists, however, are now undermining this assumption. While reasoning in a certain context may indeed help us be rational, reasoning in general is ill-equipped for truth.
So claims the Argumentative Theory of Reasoning, which is garnering a lot of attention, and deservedly so.
Here you can read the abstract of the paper:
"Reasoning is generally seen as a means to improve knowledge and make better decisions. However, much evidence shows that reasoning often leads to epistemic distortions and poor decisions. This suggests that the function of reasoning should be rethought. Our hypothesis is that the function of reasoning is argumentative. It is to devise and evaluate arguments intended to persuade. Reasoning so conceived is adaptive given the exceptional dependence of humans on communication and their vulnerability to misinformation."
Here is an excellent article on Edge about the theory:
"Reasoning was not designed to pursue the truth. Reasoning was designed by evolution to help us win arguments. That's why they call it The Argumentative Theory of Reasoning... The evidence reviewed here shows not only that reasoning falls quite short of reliably delivering rational beliefs and rational decisions. It may even be, in a variety of cases, detrimental to rationality. Reasoning can lead to poor outcomes, not because humans are bad at it, but because they systematically strive for arguments that justify their beliefs or their actions. This explains the confirmation bias, motivated reasoning, and reason-based choice, among other things."