Psychologists wonder why children can be very rational in their arguments (particularly if there is something to gain for them) yet often incapable of understanding concepts related to maths or physics. Adults too are good at reasoning in certain contexts but may be hopeless in understanding issues concerning statistics. They suggest that reasoning is not so much a trait selected over time to allow us to truly understand the essence of issues, but rather a trait selected through evolution to help us win arguments and counter those of others. Reasoning would be a way to produce effective justifications rather than to reach worthy conclusions or truths. If we cared about the truth above all, we should when necessary offer arguments that are against our own interest. The selective advantage of this strategy is that eventually two people who disagree over some issue have to compromise. The innate propensity we have to defend our point of view, even when wrong, suggests new strategies that could be adopted in schools. For example, students studying maths or physics should solve problems as a group as this would allow the reasoning errors of single individuals to be annulled.