What makes people irrational thinkers?

[Anomalocaris]

If you consider what circumstances may have led to the acquisition of the neurological tool kit that supporting thinking, I think you will agree that rational thinking can only be the result of personal experience with the use of that tool kit. In other words, we have no predilection toward rational thinking. It takes a particular way of observing or experiencing the many different outcome of thinking to arrival at a preference for rational thinking.