The TEDx talk by Dan Ariely suggests that we are not really in control of the decisions we make. Dan opines that even though we think we are making decisions, a lot of the decisions we make are actually made for us in ways we do not even realise and cannot control. He used a classic visual illusion and his own research findings to show that we are not as rational as we think we are when we make decisions.
Visual Illusion
The classic visual illusion he used was the Shepard Table illusion. 2 tables with parallelograms as their tops are placed in different positions. One vertically and the other horizontally. Due to the way our brains process the objects in three-dimensional space, we see one table as long and narrow while the other looks almost like a square. However, in actual fact, they are the same length. To prove that they are the same length, he put two red rulers on the table and we could see that they were in fact the same dimensions. But when he removed the rulers, they did not look like the same length anymore. It’s as if we had not learnt anything from the experiment.
He further suggests that vision is one of the best things that we do well as we have a huge part of our brain dedicated to it. However, if we are subject to repeatedly making the same mistakes in vision, then what is the chance we do not make mistakes in something we are not so good at.

Cognitive Illusion
He also used cognitive illusions to demonstrate how our decision making is subject to mistakes. In an experiment, he shows a graph of countries of two types of countries. Countries to the left and the others to the right. Countries on the left appeared not willing to donate their organs, while countries on the right more people were willing to donate their organs.
However, it turns out that it is a form they have to fill at the DMV that makes it appear like the countries on the left give less. The countries on the left have a form that says “Check the box if you want to participate in the organ donation programme” and they don’t check so they do not participate. Meanwhile, the countries on the right have their form that says “Check the box if you do not want to participate in the organ donation programme” and they do not check so they participate in the programme unwittingly.
Conclusion
Our decision making can be influenced by a number of factors. By the way information is presented to us, by the environment in which we have to make the decision and our previous experience. Meaning decision making has to undergo a process of critical thinking to ensure that there are little or no mistakes made.