Amodio answers some of the critical response to the Political Brain study

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).


As with most studies, this one raises more questions than it answers, and more work will need to be done. The good thing about something like this is that it'll be certain to get more funding, and the results should be expanded upon quite soon.

My studies show that libs are too stupid to bother with.

By disalushened (not verified) on 17 Sep 2007 #permalink

I tend to agree with Neurocritics general comment as it concerns knowing about differences in other brain regions along with the ACC. In fact (at least concerning research on the Stroop effect and brain imaging), the ACC seems to do everything except cook your breakfast, and no comprehensive theory has yet been proposed to explain its function. Indeed, it's function seems to vary from task to task.

One of its suggested functions (which seems to entirely change the underlying interpretation of the liberal/conservative difference and shows its connection to other brain areas) is that it appears to have a gating function. That is, it tends to decrease activity in other regions of the brain when it is highly active. In the context of the go/no go task, this would mean that to respond accurately to an appropriate letter (e.g. W), information about the letter would be selectively enhanced, while information about the inappropriate letter (e.g., M) would be blocked at a visual processing level. A higher activation of the ACC for participants indicated as being more liberal, then, could thus be indicative of a greater ability to quickly block out information deemed irrelevant for a particular task. Likewise, lower ACC activation for conservative minded persons could be attributed to reduced ability to block out information from different sources (resulting in greater 'errors'); which technically, would seem to be something more attributable to a 'liberal-minded' person.

The predominant explanation of the current study seems to be one associated with a response level of processing information. That is, the underlying assumption is that the difference between liberals and conservatives has to do with greater ability of liberals to inhibit habitual responses. However, to prove this, one would need to examine the activity of another brain region (the dpfc)which is more commonly connected with ability to inhibit habitual responses. If there is a difference in this brain region between the two political viewpoints, one would then also have to consider differences in nervous system processing speed. The difference between liberals/conservatives could be one associated with differences in personality (e.g., liberals more extraverted; conservatives more introverted), which have known connections to nervous system excitability. Or put more simply, perhaps liberal-minded students tend to play video games more than conservatives and that's why they're better at the go/no-go task.

Personally, I think the Stroop task (which actually does activate both the ACC and dpfc) would be a much better task and have greater face validity of the claim about response differences in liberals and conservatives, because it actually does measure individual differences in one's ability to overcome a habitual response (reading) in the context of a less habitual one (naming colors). The go/no go task is more of an information input screening task.

By Tony Jeremiah (not verified) on 17 Sep 2007 #permalink

I rather thought the difference was more between left or right brain recognition. The right hemisphere controls the left side of the body and the left hemishpere controls the right. Excuse the humor, but that makes the conservatives more handy and the liberals left with creativity. If we could get both sides together we might be able to use our whole mind and body politic and see a third option. Looking at both sides gives you a 3D effect like using both eyes. Maybe a third party is the answer. Only two points make a line. Three gives you some depth, not that we have no depth. Or maybe we don't.

It looks like an undergraduate project used to add a citation for the authors' citation lists. It might be suggestive, but I am surprised it was even published when one of the wings it was judging was represented by only 8 out of a sample of 43. It is just too small for meaningful conclusions to be drawn. In fact, the authors claim very little, and the furore is quite out of proportion. The reaction of the right wing is more significant than the research itself.