Beautiful, but not beguiling
A pair of psychologists at The University of Pennsylvania have highlighted a delicious irony. Sceptical neuroscientists and journalists frequently warn about the seductive allure of brain scan images. Yet the idea that these images are so alluring and persuasive may in fact be a myth. Martha Farah
and Cayce Hook
refer to this as the “seductive allure of ‘seductive allure’” (PDF
via author website).
According to Farah and Hook, brain scan images have been described as seductive since at least the 90s. Today, it’s become almost a truism that brain images are so beguiling, they paralyse our usual powers of rational scrutiny. Virtually every cultural commentary on neuroscience mentions this point as a matter of routine.
Consider two recent examples (there are hundreds more). In an otherwise wonderful essay for the New Yorker published just last weekend, Gary Marcus wrote about the rise of neuroimaging: “Fancy color pictures of brains in action became a fixture in media accounts of the human mind and lulled people into a false sense of comprehension” (emphasis added). Earlier in September, Steven Poole writing for the New Statesman put it this way: “the [fMRI] pictures, like religious icons, inspire uncritical devotion.”
What’s the evidence for the seductive power of brain images? It mostly hinges on two key studies. In 2008, David McCabe and Alan Castel showed that participants found the conclusions of a study (watching TV boosts maths ability) more convincing when accompanied by an fMRI brain scan image than by a bar chart or an EEG scan. The same year, Deena Weisberg and her colleagues published evidence that naïve adults and neuroscience students found bad psychological explanations more satisfying when they contained gratuitous neuroscience information (their paper was titled "The Seductive Allure of Neuroscience Explanations"). Not mentioned by Farah and Hook, but also relevant, is a study showing that jurors are disproportionately persuaded by brain scan evidence.
What’s the evidence against the seductive power of brain images? First off, Farah and Hook criticise the 2008 McCabe study. McCabe’s group claimed that the different image types were “informationally equivalent”, but Farah and Hook point out this isn’t true – the fMRI brain scan images are unique in providing the specific shape and location of activation in the temporal lobe, which was relevant information for judging the study. Second, a new study published this year by David Gruber and Jacob Dickerson found that the presence of brain images did not affect students’ ratings of science news stories. Finally, Farah and Hook mention research of their own and another group, as yet unpublished, involving collectively thousands of participants, which found either no effect of brain images or a miniscule effect (one of the papers has been submitted with the title “On the (non)persuasive power of a brain image.”)
So why have so many of us been seduced by the idea that brain scan images are powerfully seductive? Farah and Hook say the idea supports psychologists’ anxieties about brain scan research stealing all the funding. Perhaps above all, it just seems so plausible. Brain scan images really are rather pretty, and the story that they have a powerful persuasive effect is very believable. Believable, but quite possibly wrong. Brain scans may be beautiful but the new evidence suggests they aren't beguiling.
Farah, M.J. & Hook, C.J. (in press). The seductive allure of “seductive allure.” Perspectives in Psychological Science. (PDF via author website).