Tuesday, September 11, 2007

The Error of Prognosticating Political View by Brain Wave

Figure 1. Liberals and conservatives in the study of Amodio et al. (2007) voted primarily for Kerry and Bush, respectively, in 2004. Brain wave recordings adapted from Mathalon et al. (2002).

You've seen the headlines:
Brains of liberals, conservatives may work differently, study finds

. . .

In a study likely to raise the hackles of some conservatives, psychologist David Amodio and others found that a specific region of the brain’s cortex is more sensitive in people who consider themselves liberals than in self-declared conservatives.

The brain region in question helps people shift gears when their usual response would be inappropriate, supporting the notion that liberals are more flexible in their thinking.
And the overblown quotes:
Are We Predisposed to Political Beliefs?


"In the past, people thought that…[political leanings were]…all environmentally influenced, a combination of biological dispositions as well as cultural shaping," says David Amodio, an assistant professor of psychology at New York University. However, a new study, led by Amodio, indicates that political bent "is not just a choice people have, but it seems to be linked to fundamental differences in the way people process information."
And the baseless assertion of innate differences between the brains of liberals and conservatives:
brain neurons of liberals and conservatives fire differently [sic] when confronted with tough choices, suggesting that some political divides may be hard-wired, according a study released Sunday.
But perhaps you've read a critical analysis of the leaps of logic made in the study (and if you haven't read it, you should):
Liberal and Conservative Anterior Cingulate Cortices

. . .

Let's face it, the intro to this paper, which is necessarily short because it's only a "brief communication," is terrible. I have no idea why they hypothesized a relationship between, say, tolerance for uncertainty and conflict monitoring. That hypothesis feels about as non sequitur as this:
Given that these associations between political orientation and cognitive styles have been shown to be heritable, evident in early childhood, and relatively stable across the lifespan, we hypothesized that political orientation may be associated with individual differences in a basic neurocognitive mechanism involved broadly in self-regulation. (p. 1)
Well alrighty, then. Eye color is heritable, evident in early childhood, and relatively stable across the lifespan, but I've never seen someone associate it with self-regulation.
The Neurocritic has another ax to grind, a problem with attributing the observed results to political viewpoint and not to other factors. First, let's start out with the measures of brain activity reported in the paper. The study used EEG recordings, specifically event-related potentials. The ERP brain waves reflect electrophysiological activity recorded remotely from the scalp. While it's great for determining the temporal parameters of neural activity, it's not so great at determining where the activity is located in the brain.

One brain wave of interest here is
the No-Go N2 component, which is believed to reflect conflict-monitoring activity associated with the successful inhibition of the prepotent Go response on No-Go trials.
Another brain wave of interest is the error-related negativity (ERN), recorded at the time that people make mistakes in a task:
The response-locked error-related negativity (ERN), which peaks at approximately 50 ms following an incorrect behavioral response, reflects conflict between a habitual tendency (for example, the Go response) and an alternative response (for example, to inhibit behavior in response to a No-Go stimulus).
However, it's not at all clear that ERN reflects conflict-monitoring (Carbonnell & Falkenstein, 2006). Thus, based on a smaller-sized ERN in conservatives, one cannot conclude that they are "less responsive to conflict." In fact, if one wants to apply the logic of conflict monitoring to political viewpoint, one could say that conservatives might be more freaked out by ambiguity and conflict, since it violates their simplistic world view.

Anyway, back to the experiment. The participants in the study performed a Go/No-Go task that involved rapid responses to the letter "M" on 80% of the trials, and withholding a response to the letter "W" on 20% of the trials. The ERN was recorded when people incorrectly responded to W, and N2 was recorded when people correctly refrained from responding to W.

What were the results? Liberals showed larger ERN waves than conservatives when mistakenly responding on No-Go trials. However, so do individuals with clinical diagnoses such as obsessive-compulsive disorder (Gehring et al., 2000) or major depressive disorder (Chiu & Deldin, 2007).

Figure 2. ERN waves for liberals versus conservatives (left; adapted from Fig. 1b of Amodio et al.) and for OCD versus control participants (right; adapted from Fig. 1 of Gehring et al.).

On the other hand, individuals with schizophrenia (Mathalon et al., 2002) or psychopathy (Munro et al., 2007) show smaller ERN waves than control participants. These findings extend to the normal population, i.e., people who do not fit the criteria for a clinical diagnosis, but who score higher or lower on certain traits. For example, people who score high on negative affect have bigger ERNs (Hajcak et al., 2004), while individuals with "externalizing psychopathology"1 have smaller ERNs (Hall et al., 2007). Does this mean that liberals are neurotic and conservatives are antisocial? Since these were not assessed along with political orientation, we can only hazard a guess...


1 According to Hall et al. (2007):
Recent research examining patterns of diagnostic co-morbidity in community-epidemiological samples indicates that conduct disorder in children, antisocial behavior in adults, and substance-use disorders—along with personality traits related to behavioral disinhibition—are indicators of a common underlying vulnerability factor, labeled externalizing.


Amodio DM, Jost JT, Master SL, Yee CM. (2007). Neurocognitive correlates of liberalism and conservatism. Nature Neurosci. Published online 9 September 2007.

Political scientists and psychologists have noted that, on average, conservatives show more structured and persistent cognitive styles, whereas liberals are more responsive to informational complexity, ambiguity and novelty. We tested the hypothesis that these profiles relate to differences in general neurocognitive functioning using event-related potentials, and found that greater liberalism was associated with stronger conflict-related anterior cingulate activity, suggesting greater neurocognitive sensitivity to cues for altering a habitual response pattern.

Carbonnell L, Falkenstein M. (2006). Does the error negativity reflect the degree of response conflict? Brain Res. 1095:124-30.

Chiu PH, Deldin PJ. (2007). Neural evidence for enhanced error detection in major depressive disorder. Am J Psychiatry 164:608-16.

Gehring WJ, Himle J, Nisenson LG. (2000). Action-monitoring dysfunction in obsessive-compulsive disorder. Psychol Sci. 11:1-6.

Hajcak G, McDonald N, Simons RF. (2004). Error-related psychophysiology and negative affect. Brain Cogn. 56:189-97.

Hall JR, Bernat EM, Patrick CJ. (2007). Externalizing psychopathology and the error-related negativity. Psychol Sci. 18:326-33.

Mathalon DH, Fedor M, Faustman WO, Gray M, Askari N, Ford JM. (2002). Response-monitoring dysfunction in schizophrenia: an event-related brain potential study. J Abnorm Psychol. 111:22-41.

Munro GE, Dywan J, Harris GT, McKee S, Unsal A, Segalowitz SJ. (2007). ERN varies with degree of psychopathy in an emotion discrimination task. Biol Psychol. 76:31-42.

ADDENDUM: Cognitive Daily has just posted another critique of this paper, The claim: Politically liberal brains are better at handling change

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At September 14, 2007 2:20 PM, Anonymous Anonymous said...

This study used 43 research subjects, 11 of whom were slightly to moderately conservative. The study did not include any subjects who were ranked as 5 out of 5 on the conservative scale. There were no controls on age, sex (even though 27 of the subjects were women), IQ, or mental illness.

How one can may such sweeping conclusions on such thin data unless one has an ax to grind?

P.S. In a previous paper the authors say the "core dimensions of conservative though" are "resistance to change and support for inequality."


At September 14, 2007 3:28 PM, Blogger The Neurocritic said...

Anonymous, it seems you didn't read my post. I was in fact quite critical of the paper here and in the next entry. However, I do not think the authors are charlatans. I place part of the blame on the editors at Nature Neuroscience for accepting the paper in its current form.


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