What are systematic deviations from rationality?

Systematic deviations from rationality are like when your brain makes the same silly mistakes over and over again, even when you know better.

Imagine you have a favorite toy that you always take to school. Every day, you put it in your backpack, but sometimes you forget it. You know you should remember it, but you still forget it every time. That’s like a systematic deviation from rationality, your brain keeps making the same mistake again and again.

Your brain is like a busy little robot that tries to make things easy for you. Sometimes it takes shortcuts. For example, if you're hungry and see a cookie on the table, your brain might say “I should eat the cookie later,” but then you forget about it, and end up eating it right away! That’s a systematic deviation because your brain keeps doing this same thing when it's easy.

These little mistakes are normal, and they help your brain save energy. But sometimes they make you act in ways that don’t seem very smart, even though you're not being lazy or silly on purpose.