David Amodio and his colleagues have taken a lot of heat across the internet for their recent brief report on brain and behavior correlation with political views (see here for one of the more strident pundit reactions). The Neurocritic was able to track down Amodio himself and get his responses to some more serious criticism:
People have complained that there were more liberals the conservatives in the sample. True, in an absolute sense. But this is typical in political psychology: Americans are more conservative on average, and so more extreme conservatives usually rate themselves as moderate conservatives, whereas moderate liberals tend to rate themselves more extremely (see Linda Skitka’s work and comments on the paper). It’s a scaling issue that psychologists deal with all the time.
Nevertheless, we’re talking about a correlation. The clear linear effect suggests the stronger liberalism is associated with greater conflict-related ACC activity. Not sure how anyone can argue with that.
Amodio addresses several other points in his response, so it’s worth a read. But the Neurocritic has a lingering complaint:
My closing remarks are based on the assumption that the error-related negativity (ERN) brain wave is a direct measure of conflict monitoring in the anterior cingulate cortex (ACC). [I’ve focused on the ERN rather than the N2 because the former is illustrated in the paper and the latter is not.] A quick review of the literature indicates that’s not necessarily the case. First, not everyone agrees that the ERN measures response conflict rather than error processing more specifically (Carbonnell & Falkenstein, 2006), or that ACC hemodynamic activity during error commission is a reflection of response conflict (Critchley et al., 2005; Garavan et al., 2003). Second, when people make mistakes, it seems that more of the brain is active than just the ACC (Klein et al., 2007; Ullsperger & von Cramon, 2006).
What he’s saying here is that Amodio et al.’s conclusion about the liberal/conservative difference in the study is not necessarily traceable to a single area of the brain. It’s a reasonable point to make, since the EEG analysis can only be done by extrapolation: EEG measures electrical activity on the surface of the head, and then determines where that activity originated. It’s not as accurate as an fMRI, but it does have the advantage of being able record changes that occur over a shorter time period. But in Amodio’s defense, clearly liberalism correlates with different brain activity during the task, regardless of the origin of that activity. An interesting debate.
Meanwhile Slate’s William Saletan claims the study was “rigged” on the basis of his non-expert reading of the study. Among his talking points:
An “ms”–millisecond–is one-thousandth of a second. That means participants had one-tenth of a second to look at the letter and another four-tenths of a second to hit the button. One letter, one-tenth of a second. This is “information”?
Yes, it is “information,” Mr. Saletan. What other definition of “information” do you propose? Can you provide any information to support your headline’s claim that the study was rigged?
I don’t think the study was rigged, but I do agree with Saletan on some of the other points he brings up. This study doesn’t offer much in the way of explaining the real differences between liberals and conservatives. It’s simply interesting that there are differences that can be seen at this level (in college students, anyways — I’d be interested to see if the effect persists in older adults).