One-Sided vs Two-Sided Messages
What kind of arguments are more effective: one-sided or two-sided? One-sided messages mention only your point; two-sided arguments also acknowledge counter-points. Research shows two-sided messages are usually more effective. So normally, your messages will be more effective if they acknowledge the counter-arguments and refute them.
Effectiveness of Two-Sided War Propaganda
The first study on one-sided vs two-sided messages was part of seminal experiments by Carl Hovland and his colleagues during the World War II. The U.S. War Department asked the Hovland’s group to test persuasiveness of various broadcasts aimed at the American soldiers. For example, one message wanted to convince American soldiers that the war with Japan, after Germany’s defeat, wouldn’t be easy but eventually the Americans would prevail. One-sided radio broadcast simply said that the war with Japan would continue for two more years but ultimately Japan would suffer defeat. The two-sided argument added opposing arguments and refuted them.
The one-sided argument persuaded more if soldiers already agreed with the message. However, those who disagreed with the main point were more persuaded by the two-sided argument.
Effectiveness of Two-Sided Recycling Appeals
In a relatively recent study, Carol Werner and her colleagues tested persuasiveness of aluminum-can recycling signs. A one-sided appeal stated
“No Aluminum Cans Please!!! Use the Recycler Located on the First Floor, Near the Entrance.”
Two-sided appeal added:
“It May Be Inconvenient , But It Is Important!!!!”
The two-sided appeal was the most effective: recycling reached 80%, doubling the rate of one-side message.
Meta-study on One-sided vs Two-sided Messages
A meta-study on persuasiveness of one-sided vs two-sided messages concluded that two-sided messages are more persuasive, but only if they not just mention opposing arguments, but also refute them.
- Hovland, C. I., Lumsdaine, A. A., & Sheffield, F. D. (1949). Experiments on mass communication. Studies in social psychology in World War II (Vol. III).
- O’Keefe, D. J. (1999). How to handle opposing arguments in persuasive messages: A meta-analytic review of the effects of one-sided and two-sided messages. In M. E. Roloff (Ed.), Communication Yearbook 22, 209-249.
- Werner, C. M., Stoll, R., Birch, P., & White, P. H. (2002). Clinical validation and cognitive elaboration: Signs that encourage sustained recycling. Basic and Applied Social Psychology, 24, 185-203.