Ben Goldacre, The Guardian, Saturday 30 October 2010
When the BBC tells you, in a headline, that libido problems are in the brain and not in the mind, then you might find yourself wondering what the difference between the two is supposed to be, and whether a science article can really be assuming – in 2010 – that its readers buy into some strange form of cartesian dualism, in which the self is contained by a funny little spirit entity in constant pneumatic connection with the corporeal realm.
But first let’s consider the experiment they’re reporting on.
As far as we know (this experiment has not yet been published, only presented at a conference) some researchers took seven women with a “normal” sex drive, and 19 women diagnosed with “hypoactive sexual desire disorder”. Participants watched a series of erotic films in a scanner while an MRI machine took images of blood flow in their brains: the women with a normal sex drive had an increased flow of blood to some parts of their brain associated with emotion, while those with low libido did not.
Dr Michael Diamond, one of the researchers, tells the Mail: “Being able to identify physiological changes, to me provides significant evidence that it’s a true disorder as opposed to a societal construct.” In the Metro, he goes further: “researcher Dr Michael Diamond said the findings offer ‘significant evidence’ that persistent low sex drive – known as hypoactive sexual desire disorder (HSDD) – is a genuine physiological disorder and not made up.”
This strikes me as an unusual world view. All mental states have physical correlates, if you believe that the physical activity of the brain is what underlies our sensations, beliefs and experiences: so while different mental states will be associated with different physical states, that doesn’t tell you which caused which. If I do not have the horn, you may well fail to see any increased activity in the part of my brain that lights up when I do have the horn. That doesn’t tell you why I don’t have the horn: maybe I’ve got a lot on my plate, maybe I have a physical problem in my brain, maybe I was raped last year. There could be any number of reasons.
But far stranger is the idea that a subjective experience must be shown to have a measurable physical correlate in the brain before we can agree that the subjective experience is real, even for matters that are plainly experiential. If someone is complaining of persistent low sex drive, then they have persistent low sex drive, and even if you could find no physical correlate in the brain whatsoever, that wouldn’t matter, they do still have low sex drive.
Interestingly, this odd interpretation is far from new: in fact it’s part of a whole series of recurring themes in popular misinterpretations of neuroscience, first described formally in a paper from Nature Reviews Neuroscience called “fMRI in the public eye”. To examine how fMRI brain imaging research was depicted in mainstream media, they conducted a systematic search for every news story about it over a 12 year period, and then conducted content analysis to identify any recurring themes.
The first theme they identified was the idea that a brain imaging experiment “can make a phenomenon uncritically real, objective or effective in the eyes of the public”. They described this phenomenon as “neuro-realism”, and the idea is best explained through their examples, which mirror these new claims about libido perfectly.
So an article in the Washington Post takes a view on pain, and whether the subjective experience of it is enough: “patients have long reported that acupuncture helps relieve their pain, but scientists don’t know why. Could it be an illusion?” They have an answer. “Now brain imaging technology has indicated that the perception of pain relief is accurate.”
Another says that brain imaging “provides visual proof that acupuncture alleviates pain”. The reality, of course, is much simpler: for your own personal experience of pain, which is all that matters, if you say that your pain is relieved, then your pain is relieved (and I wish good luck to any doctor who tells his patient their pain has gone, when it hasn’t, just because some magical scan says it has).
The New York Times takes a similarly strange tack in a brain imaging study on fear: “Now scientists say the feeling is not only real, but they can show what happens in the brain to cause it.” Many people find fatty food to be pleasurable, for the taste, the calories, and any number of other reasons. When a brain imaging study showed that the reward centres in the brain had increased blood flow after subjects in an experiment ate high-fat foods, the Boston Globe explained: “Fat really does bring pleasure.”
They’re right, it does. But it’s a slightly strange world when a scan of blood flow in the brain is taken as vindication of a subjective mental state, and a way to validate our experience of the world.
And another thing:
No space to weave it in (the column was over length already, I can’t bring myself to look at what went in the paper) but the other relevant theme here is the medicalisation of sex, if you’re interested in more there’s a good interview with Ray Moynihan on Pharmalot, I wrote about the medicalisation of everyday life here and in these, and Petra is often good on it here. Lastly Neuroethics wrote on this study and dualism.