Behaviour Change

PROPAGANDA FOR CHANGE is a project created by the students of Behaviour Change (ps359) and Professor Thomas Hills @thomhills at the Psychology Department of the University of Warwick. This work was supported by funding from Warwick's Institute for Advanced Teaching and Learning.

Friday, November 4, 2016


“There's not a liberal America and a conservative America; there's the United States of America.” Barack Obama.

Being one of the most influential men in the world, Obama has inspired and persuaded many people during his time as President. With his eight years in power soon coming to an end, it seems appropriate to look back at where it all began.

On July 27th 2004, Obama took to the stage at the Democratic National Convention to give the keynote address. It is this speech that projected Obama from being a small name, only known by a few political circles, into a potential world leader. Obama managed to capture the attention of the nation by injecting hope, belonging and truth into the country. The overwhelming reaction from this speech allowed Obama to defeat Alan Keyes for the Senate seat and later become the 44th President of the United States of America on November 4th, 2008. 

Why was this speech so effective? 

1. Common ground

[Tonight, we gather to affirm the greatness of our nation not because of the height of our skyscrapers, or the power of our military, or the size of our economy; our pride is based on a very simple premise, summed up in a declaration made over two hundred years ago: "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain inalienable rights, that among these are life, liberty and the pursuit of happiness.”]

According to Carnegie (2010), if you want to persuade someone, then you should find a common interest. People are more likely to listen and engage with a message if they think it is relevant to them. Obama creates relevance to his audience by implying he is the same as all Americans, emphasising his background and interests. This insinuates he knows what the nation wants, so therefore can make a difference. 

Evans (1963) carried out a study that illustrates the effectiveness of similarity as a persuasion technique. When reviewing the sale records of car insurance companies, it was found that customers were more likely to purchase insurance when the salesperson was similar in age, religion, politics and smoking habits to themselves. This is proof that similarity influences persuasion — the more we relate to others the more they will be persuaded, as it consequently leads to interest and interaction.

 2. Repetition

[…there's not a liberal America and a conservative America; there's the United States of America…There’s not a black America and white America and Latino America and Asian America; there's the United States of America.]

Repetition has been used as a persuasion technique for decades. The more familiar we are with something, the more we like it (Zajonc, 1968). Obama cleverly uses repetition to increase familiarity of the points he is trying to make, which consequently leads to liking and persuasion.

A study which demonstrates the use of repetition was created by Cacioppo and Petty (1989).  Participants were required to listen to an audiotape, either once or three times. Following this, participants filled out a questionnaire regarding the quality of the audiotape. The results revealed that message repetition can increase persuasion of a strong argument and decrease persuasion of a weak argument by enhancing argument analysis, as seen in Figure 1. This is evidence that repetition leads to liking, which in turn leads to greater social influence. We are often unaware that our opinion has been changed by repetition, making it a very powerful technique. Increase in scrutiny of Obama's speech due to repetition, therefore increased persuasion as it was a strong argument.

Figure 1: Average agreement level for strong argument (left charts) and weak argument (right charts) after 1 or 3 exposures.

3. Social proof

The speech was broadcast to approximately 9.1 million people.  Those who watched would have seen an arena full of people holding Obama banners. This would have acted as social proof to viewers that Obama is credible, due to the fact that he appears to have a lot of supporters. This then links to social norms, if other people are following Obama than we subconsciously think we should too. 

Bandura and Menlove (1968) conducted an experiment which demonstrates the power of social proof. Children who were afraid of dogs were able to reduce their fear by watching a clip of another child playing with a dog. Videos were just as effective as watching a live demonstration (Bandura, Grusec & Menlove, 1967).  Children's fear was most effectively lowered when the video clips demonstrated a variety of children playing with their dogs, as seen in Figure 2. Social proof therefore has the most impact when proof is depicted by many people, hence why Obama’s speech was so effective, as he had thousands of supporters present.

Figure 2: Median approach scores pre-test, post-test and follow up after viewing a single model interacting with a dog, multiple models interacting or control.  

Ten years on and Obama’s speech is still being talked about. Imagine if these persuasion tactics had not been used, Obama may not have been President and we may not have witnessed such an impressive man take control of such a powerful country.


Bandura, A., Grusec, J. E., & Menlove, F. L. (1967). Vicarious extinction of avoidance behavior.   Journal of personality and social psychology, 5, 16.

Bandura, A., & Menlove, F. L. (1968). Factors determining vicarious extinction of avoidance behavior through symbolic modeling. Journal of personality and social psychology, 8, 99.

Cacioppo, J. T., & Petty, R. E. (1989). Effects of message repetition on argument processing, recall, and persuasion. Basic and Applied Social Psychology, 10, 3-12.

Carnegie, D. (2010). How to win friends and influence people. Simon and Schuster.

Evans, F. B. (1963). Selling as a dyadic relationship-A new approach. The American Behavioral Scientist, 6, 76-79.

Zajonc, R. B. (1968). Attitudinal effects of mere exposure. Journal of personality and social psychology, 9, 1.

Emma Horton

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