Persuasion and the ‘Poison Parasite’

A great deal of psychology research has focused on the mechanics and effects of persuasion. But what about the flip side: What techniques and strategies do we have to resist persuasion when it is unwelcome?


Observer photo by Mel Hill

Cialdini presents the APS William James Distinguished Lecture at the May 2001 MPA meeting.

Robert Cialdini and colleagues at Arizona State University have studied the elements of counter persuasion and have developed models designed to puncture an opponents’s messages, be they political campaign ads or self-serving commercials. Cialdini described his findings in his APS William James Distinguished Lecture at the 2001 Midwestern Psychological Association (MPA) meeting earlier this year. The APS William James lectures are intended to bring the best in psychological science to regional psychology meetings. Other William James speakers have included Stephen Ceci, John Jonides, and Sam Glucksberg.

In a presentation entitled “The Poison Parasite Defense: A New Way to Sap a Competitor’s Persuasive Strength,” Cialdini said the literature on resisting persuasion is relatively sparse, but one conclusion “rises to the top. If we want people to resist an argument we think is deceptive or duplicitous, the best strategy is appropriate and accessible counter arguments.”

Sounds pretty straightforward, right? But think about it-exactly how do you divert an audience and shift the focus to your arguments and away from an opponent’s more dominant voice? Much easier said than done, notes Cialdini, especially when the other side has greater access to the minds of the audience by virtue of having more resources, an existing relationship, or closer proximity to the targeted group.


Cialdini found that successful counter ads involve the use of effective counter-arguments that call into question the opponent’s facts and trustworthiness; mnemonic links to the opponent’s ads, a parasitic device which essentially infects the opponent’s message by linking its memory and impact to the counter ad; and ridicule to satirize the opponent’s ads.

An example of a successful ad campaign that involved all of these elements was the anti-smoking campaign some years ago that featured mock “Marlboro Man” commercials. Those commercials initially looked like tobacco ads, with the same rugged outdoor settings and same macho cowboy characters. But the counter ads then transformed into attacks on tobacco, depicting the cowboys coughing and displaying other health symptoms that result from smoking. This undermined the original ads, as Cialdini said, the satirical ads “preposterized” the notion that smoking was linked to images of male strength and potency.


In one study, Cialdini’s research team used political campaign ads to gauge the relative importance of ridicule, counter arguments, and mnemonic links. Study participants viewed a mixture of actual political ads and research-designed counter-ads that contained combinations of the elements (i.e., some contained all three elements), while others contained just one of the elements or pairs of elements. Returning after a week of seeing the ads, participants were again shown the original ad and asked whether they would vote for that candidate. The evidence was overwhelming: The “poison parasite” ad – so labeled because it contains two elements, one poisonous (the counter argument) and one parasitic (the mnemonic link) – was found to be very powerful both by itself and with an element of ridicule, in reducing the effects of the original ad and in affecting people’s attitudes. The researchers detected no influence from the ads featuring just a counter argument or just ridicule alone.

A second study involved ads in which oil or utility companies portrayed themselves as having positive impacts on the environment. “These are clearly self-serving,” said Cialdini. “Unless countered, they can seep into peoples’ attitudes.”

The results of this second study were similar to the first one. The poison parasite combination was significantly more effective than counter arguments alone in weakening the credibility of the environmental ads.

The poison parasite is a potentially powerful tool, said Cialdini, one that can also enforce high ethical standards simply by the potential to expose misleading messages. At the same time, he added, those who use the poison parasite must also be honest or they too will lose credibility.

While his research indicates that success does not seem to rely on ridicule, the converse is true, according to Cialdini, who said that “ridicule’s classic forms embody the poison parasite.”

“Ridicule is the best test of truth” – a quote Cialdini attributes to Lord Chesterfield. “The more we can puncture an argument, the less truthful it is,” he said.

Cialdini pointed out that his studies don’t necessarily rule out the impact of ridicule in creating an effective counter ad; they simply confirm the importance of the other two elements. But, he said, ridicule by itself has problems because it can be perceived as dishonest or less credible.

Don’t miss Robert Cialdini’s Keynote Address at the APS Convention in New Orleans, June 6-9, 2002. For more information on the annual convention, please visit the APS website at

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