President Obama's failure to speak out repeatedly on the urgency of climate action is his biggest communications mistake. If our leaders don't talk about an issue, it generally won't become sufficiently salient for either the media or the public.
But Obama's statement at the Democratic convention -- responding to Romney's mockery of his 2008 pledge of climate action -- also contained a classic messaging mistake:
And yes, my plan will continue to reduce the carbon pollution that is heating our planet -- because climate change is not a hoax. More droughts and floods and wildfires are not a joke. They're a threat to our children's future. And in this election, you can do something about it.
The social science literature is quite clear that repeating a myth is not the best way to debunk it. Indeed, there is evidence that it can actually end up promoting that myth.
It's why linguist George Lakoff titled his best-selling book, Don't Think of An Elephant. If I say that to you, you will think of an elephant. Negatives carry very little rhetorical weight. In this case, the word "hoax" is very strong and memorable and is not one that should be repeated by those who understand the realities of climate science.
As I discuss in my book, Language Intelligence: Lessons on Persuasion from Jesus, Shakespeare, Lincoln, and Lady Gaga, this notion is so core to rhetoric that the ancient Greeks even had a figure of speech named for it -- apophasis. Apophais, from the Greek word for "to deny," is the figure of speech that emphasizes a point by pretending to deny it, that stresses an idea or image by negating it. As Shakespeare has Marc Antony say to the Roman citizens in the "Friends, Romans, Countrymen" speech after Caesar's assassination, "Sweet friends, let me not stir you up to such a sudden flood of mutiny." He wants -- and gets -- a mutiny.
This is not just a long-standing principle of rhetoric, but something demonstrated by modern social science research. In one 1990 study, undergraduate students observed sugar from a labeled commercial container as it was poured into two bottles. They then labeled one bottle "sugar" and the other "Not Sodium Cyanide." Students avoided eating sugar from the second bottle even though they had watched it being poured and "even though they had arbitrarily placed that label on it" and knew the label was accurate -- that it was not sodium cyanide. Such is the power of words or, rather, the insidious lack of power of the word 'not.'
Even more insidious, "when people find a claim familiar because of prior exposure but do not recall the original context or source of the claim, they tend to think that the claim is true," as noted in a 2005 journal article, "How Warnings about False Claims Become Recommendations," which concluded
Telling people that a consumer claim is false can make them misremember it as true. In two experiments, older adults were especially susceptible to this "illusion of truth" effect. Repeatedly identifying a claim as false helped older adults remember it as false in the short term but paradoxically made them more likely to remember it as true after a 3 day delay. This unintended effect of repetition comes from increased familiarity with the claim itself but decreased recollection of the claim's original context. Findings provide insight into susceptibility over time to memory distortions and exploitation via repetition of claims in media and advertising.
When the Centers for Disease Control and Prevention put out a flier to debunk myths about the flu vaccine, it repeated several myths, such as, "The side effects are worse than the flu" and labeled them false. A study of people given the flier found that "within 30 minutes, older people misremembered 28 percent of the false statements as true." Worse, "three days later, they remembered 40 percent of the myths as factual." And they identified the source of their erroneous beliefs as the CDC itself!
A Washington Post article, "Persistence of Myths Could Alter Public Policy Approach," explained, "repetition seems to be a key culprit. Things that are repeated often become more accessible in memory, and one of the brain's subconscious rules of thumb is that easily recalled things are true."
Another useful article is " 'I am not guilty' vs 'I am innocent' " by Ruth Mayo et al in The Journal of Experimental Social Psychology in 2004, which found that for many people, the "negation tag" of a denial falls off with time:
"If someone says, 'I did not harass her,' I associate the idea of harassment with this person," said Mayo, explaining why people who are accused of something but are later proved innocent find their reputations remain tarnished. "Even if he is innocent, this is what is activated when I hear this person's name again."If you think 9/11 and Iraq, this is your association, this is what comes in your mind," she added. "Even if you say it is not true, you will eventually have this connection with Saddam Hussein and 9/11."
Mayo found that rather than deny a false claim, it is better to make a completely new assertion that makes no reference to the original myth.
If you want to debunk a myth, you should focus on stating the truth, not repeating the myth.