Inspired by  Thinking Fast and Slow - Daniel Khanemam 

Psychologist Eckhard Hess was the one who described the pupil of the eye as a window to the soul . He noticed that pupils are sensitive indicators to mental effort that means if we are concentrating on something , working hard to do it , our pupils will be in a dilated state . While if we our doing something routine and casual in nature our pupil will be in normal state . 

One of the experiments conducted by Daniel Khanemam and his team was the solving of multiplication problems. The participants were given difficult multiplication problems to solve . Whenever the participants tried to solve it their pupils dilated and when they reached the answer or gave up immediately their pupils returned to normal state . 

You must have gone through an experience where you are engrossed in something and you just can't hear someone calling you . That the state when your SYSTEM2( as discussed in previous blog )  is working overtime and your pupils are in dilated state. 

The pupil is like the electricity meter installed in our houses.  Just like the electricity meter gives us the reading of electricity consumed , our pupils inform us about the mental effort applied . More the mental effort more is the dilation . Just as there are different appliances in our house which consume electricity our brains have different parts which require energy . 

Did you ever notice that if we start something new eg solving maths equations , in the beginning we are not good at it , it takes us time to solve the equations. This is the state when maximum part of the brain is being utilised in solving the equations. Thus maximum energy is being spent on the same activity and our pupils are in dilated state. As we get used to solving equations, we solve them easily . Thus less energy is used and our pupils don't dilate that much . Thus it's observed that intelligent people generally have to use less energy , or smaller part of the brain for doing something as compared to normal people.  This is the Law of Least Effort. Eventually everyone follows this law , we always like to do things in a way which will require least effort. 

Now let's discuss about Priming . Have you seen some mentalist  magic shows on YouTube? There the magician writes something down on paper about what you will say and gives it to the you . Then questions you and you give the exact same answer which is written on the piece of paper . 

Well this is type of priming effect. 

For eg complete this word for me - SO_P. 

Now if you have done any activity which is associated with eating or subconsciously  are thinking about eating, or seen anything on TV related to eating etc  then you will write SOUP . 

But if have have taken a bath or seen an add of washing powder etc you will write SOAP. Our brain does this without us consciously thinking about it . This is called the priming effect where things around us influence our brain subconsciously without us noticing and we react accordingly. Ever wondered why in some countries we have huge posters of the great leader almost I'm every corner of the road. This way people subconsciously have an idea of the great leader watching us and knowingly or unknowingly it's always in their head.