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As humans, we have always prided ourselves on our rationality. Since Aristotle defined us as ‘rational animals’, philosophers have praised humans for their logic and reason. Carl Linnaeus, the father of modern taxonomy, christened us Homo sapiens, or ‘wise man’. Some scientists argue that we are so closely related to chimpanzees that we should all be included in the same genus. And yet we still consider ourselves special, separate, standing alone in the genus Homo. It’s more arrogant than Trump thinking he can successfully run the United States.

But are we as wise and rational as history would have us believe? And if so, why do we let children die in sweat shops, start wars we cannot end and destroy our climate with fossil fuels? Perhaps most perplexing is that despite humanity’s clear flaws, we are all convinced we are right. Supporters of every political party believe that theirs is the best option, painting the opposition as immoral and incompetent. Advocates on either side are certain of their own position, whether the debate concerns abortion, same sex marriage or euthanasia. People deny climate change, evolution or the efficancy of vaccinations, sometimes at a great cost to themselves and others. I could list dozens more emotive and controversial issues, but it is the same each time, both sides have an unshakable belief in their position.

Decades of research into human behaviour has begun to explain this, painting a very different picture to the infallible ‘wise man’ of the 1700s. We are not the rational creatures we thought we were. Behavioural economist and Nobel Laureate, Daniel Kahneman, explains this by identifying two different ways of thinking in his book Thinking, Fast and Slow. Our default thought process, or ‘System 1’, is fast and instinctive. It relies on pattern recognition and intuition to make rapid decisions, often unconsciously. On the other hand, ‘System 2’ is slow, conscious, and relies on logic and reason. System 2 is what we like to imagine determines our behaviour, but more often it is System 1 that makes our decisions.

Intuition is fantastic for everyday choices, like deciding whether to buy coffee from House of Cards or Ho Ho’s. It also helps us act quickly to avoid a threat, like campaigners in student elections. But it renders us vulnerable to bias when considering complex issues. Confirmation bias, where we only pay attention to information that supports our current beliefs, is an example of System 1 influencing our rational side. System 1 is also responsible for the ‘backfire effect’, where providing someone with evidence that contradicts their belief strengthens their view.

You can show a climate change denier all the evidence in the world, and they will still walk out on a wintery day and claim that because it is cold, climate change is therefore, not happening. These biases occur because our brains are big fans of ‘cognitive ease’. We are more likely to believe something that feels familiar, is easy to compute and can be incorporated into our personal narrative – regardless of if it is supported by fact. Changing your beliefs is hard, and may require changes in your identity and behaviour. It’s no wonder we stick to what (we think) we know.

If these thought processes prevent us from seeing the truth, then why did they evolve? How did the ‘wise man’ rise to power if he wasn’t so ‘wise’ after all? Before civilisation and technology protected us from the dangers of predators and starvation, truth was not as important as immediate survival. Rapid decisions were needed to avoid attacks, obtain food and compete for mates. Our biases exist because they have saved lives, we assume everything has a cause (even when it doesn’t) because it is safer to assume a lion caused that rustling noise than to wait and see if it was just wind. We rarely change our minds because it is safer to appear confident than it is to be right. It is safer to make assumptions than to expend precious energy trying to find the truth.

There are still advantages of System 1 in our modern lives. But with such a large population, and such influence on the world around us, the consequences of being wrong are greater now than they were 100,000 years ago. Unfortunately, our thought processes haven’t had time to adapt to this rapid change, and we cannot change them. But hopefully, by learning about our own biases, we can compensate for our faulty ‘intuition’.