It is difficult to think of your behaviour as being directed by forces outside of your control. The idea that you are not an autonomous individual creating judgements independently is something that is difficult to accept.
Unfortunately for our ego, there are hundreds of psychological studies that prove our opinions, thoughts and actions are not entirely our own.
Whilst reading Thinking Fast and Slow I came across an interesting psychological concept known as priming. In short, the idea is that you can prime somebody to give a particular answer by exposing them to stimulus before hand. You can try it yourself – casually talk to somebody about their lunch, ask them what they ate and then ask them to fill in the missing letter in ‘SO_P’. It is likely they will choose ‘SOUP’. Try it with somebody else but talk to them about bathrooms, cleaning and showers then it is likely they will opt for ‘SOAP’.
The term goes back to a study in 1996 by John Barge who demonstrated that making people think of old age during a word game made them walk around more slowly afterwards.
There are tonnes of examples of priming given in the book and across the web. A picture of eyes will make people more honest and thoughts of money make people more antisocial and less likely to help other people.
Of course, the concept of priming has an important effect on the role of the media. Issues that are given a high prominence in the media will be primed in peoples mind come election day.