Visual illusions can be a metaphor for rationality. When an illusion is proven to just be a trick, your intuition fools you in a repeatable predictable way and there is no way around it. Vision is the best thing that Humans can do. We have been evolutionarily designed to use our sight. If illusions can trick our best sense then it is not hard to imagine that if we are making mistakes in something we are so good at then what are the chances that we dont make mistakes in other areas that we are not as good at? Things that we dont have an evolutionary reason to do with no specialized part of the brain like vision has and something we dont spend many hours of the day doing. We may make many more mistakes and not even realize that we are making them. Cognitive illusions are harder to demonstrate than visual illusions. For an example, organ donor percentage in European countries can be seperated into two groups, countries that have a very high percentage of donors and countries with very low percentages of organ donors. When asked some thought it had something to do with cultural issues or it had to do with how much the people cared about society or maybe that it was about religion. However, the graph shows countries that are thought to be very simple but demonstrate different behaviors. It turns out it actually has to do with the forms that the people must fill out at the DMV. The forms in the countries with low numbers of donors have a choice that says "check the box below if you want to participate in the organ donor program." What happens is people dont check the box so they dont join. The countries that have a lot of donors have a form that says, "Check the box below if you dont want to participate in the organ donor program." When people get this they dont check but they do join. This means that even though we feel like we make all the decisions in our lives ourselves, many of our decisions are nit residing within us. The person that designed the form will have a huge influence in what you will do. You might think that if you were to encounter one of those forms that you would change your behavior but you have such a feeling that you are in control of your own behaviors that it is very hard to believe that we actually have an illusion of making a decision. Some may think that this happens because it's something no one really cares about and it's after you're dead so it doesn't effect you, but in reality its exactly the opposite. It is because we care and it is such a complex desicion that we dont know what do do so we leave the box blank and we pick whatever it is that was chosen for us. This is also examined when making decisions of different kinds. For example the choice between an all expence paid trip to Rome or and all expence paid trip to Paris. They are both different but it is difficult to choose. Then if you introduce a choice that is inferior to one of the other choices it is much easier. If you have the choice between an all expence paid trip to Paris and two seperate trips to rome except one of the trips does not include coffee with breakfast then the trip that does include coffee with breakfast suddenly becomes the superior choice and even begins to look more superior to paris. It is the same with physical attraction. An experient was done where a group of people were asked to pick between two faces to take on a date but half of the group was given those same two faces with a third face that was similar to one of the other faces but slightly uglier. This was to see whether the uglier version would work in favor of the more attractive person and it was true. This is usually how people pick someone to take bar hopping. They choose someone that looks similar to them but a little uglier. When we build physical things we understand our limitations and we buld around them. when it comes to the mental world such as designing things like healthcare, retirement and the stock markets we forget our limitations. If we understand our cognitive limitations in the same way we understand our physical limitations we could design a better world.