Most parents who caught their young teenager smoking despite warning of the danger would think little of the defense that "my best friend's grandfather smoked his whole life and he never got cancer!" Yet adults often use the same tactic: argument by anecdote. Those who plow money they don't have into gambling readily recall the truck driver who hit the lottery jackpot. Those opposed to vaccination tell about the child diagnosed as autistic just weeks after his last DPT shot. Those demanding stronger gun laws remind us of the child accidentally shot by her little brother with Daddy's nearby 9 mm, just as those who oppose such laws cite the woman who fended off a home invader with her Glock.
This approach is especially popular in the hands of politicians. The argument for a wall along the Mexican border is justified by the horrible death of San Franciscan Katie Steinle at the hands of Juan Francisco Lopez-Sanchez, who had been previously deported five times. The argument for accepting refugees from majority-Muslim countries is made using the case of Hameed Khalid Darweesh, who worked a decade in Iraq for the U.S. as an interpreter.
Anecdotes are emotionally compelling stories, which is why we tell them. From the standpoint of evolutionary biology, they played a powerful role in advancing our species, transmitting survival lessons before written language or history. With young children, this purpose is still valuable. Indeed, we live by stories. If a picture is worth a thousand words, a story is worth many pictures. It wraps information, values, norms, and lessons learned into a concise packet much easier to remember and share than disjointed facts.
Anecdotes also serve a purpose in bringing problems to our attention. If we never heard the story about Etan Patz, we might never have become sensitized to the nationwide problem of missing children. But not every story signifies the accurate extent of a problem (or proposed solution). The story about the San Bernardino terrorists may lead us to believe that all immigrants from majority-Muslim nations are potential threats, even though there is no evidence of that, including the fact that one of the shooters was American-born.
Thus, stories have their drawbacks, which we must keep in mind. Those who abuse the power of stories either forget or, more ominously know, these dangers. We must not allow the simplicity of a story to substitute for careful thinking, which is much harder.
A powerful, emotional story can fix an idea in our heads that is hard to dislodge. "Affect is a strong conditioner of preference," the behavioral psychologist Paul Slovic said. It makes us prone to believe whatever comes along with the story. This emotional connection also makes us prone to confirmation bias, by which we look for evidence that supports our views rather than contradicts them.
A story, in the hands of a propagandist is a powerful tool of persuasion. Behavioral economists Amos Tversky and Daniel Kahneman coined the term the "availability heuristic" for the tendency of a story at hand to take on far more weight in our decision making than information that is more physically or psychologically distant.
Stories can also skew our thinking because they are single data points which may not represent the broader situation. The story of one man "saved" by the Affordable Care Act's provisions is not sufficient to draw conclusions about the impact of the law, which ought to be based on far more rigorous and statistically supportable data. We need to remember that stories often get attention because they are outliers, not because they are typical. To cite another example, relying on extremes leads many modern parents, horrified by the occasional story of an abducted child, to believe that the world is much more dangerous for kids than when they were children; yet, for most, it has gotten safer.
Stories can also lead to short-sighted moral reasoning. The ethicist Peter Singer points out how we are much more willing to give to a named person whose story we heard on social media than to unnamed thousands in more abject poverty in distant lands.
Still further, especially in the formation of political positions, for every story there is an equal and opposite story. Tell me about the woman on welfare who sold food stamps to get money for drugs, and I can tell you about the working mother for whom food stamps kept her children from malnutrition. Dueling stories may make for committed followers, but they seldom make for sound social policy.
Storytelling serves us well, except when it doesn't. The capacity to use stories is an important human trait, but stories in the wrong hands or used without awareness of their limits are dangerous. Stories may start us thinking, but they should not end that thinking. The more we remember this, the more we will make better decisions.