Monday, January 28, 2019

Evolution of empathy, part II

Medical students, Monterrey (credit: Daniel Adelrio, Wikicommons). Mexicans feel more empathy if they have a university degree. Does university make people more empathic?

We differ from individual to individual in our capacity not only to understand how others feel but also to experience their pain or joy. This “affective empathy” also differs between the sexes, being stronger in women than in men. Does it also differ between human populations? It should, for several reasons: 

- Affective empathy is highly heritable. A recent study put its heritability at 52-57% (Melchers et al. 2016).

- It differs in adaptiveness from one cultural environment to another, being adaptive in high-trust cultures and maladaptive in low-trust ones. There has thus been a potential for gene-culture coevolution.

- Such an evolutionary scenario would require relatively few genetic changes. Affective empathy exists in all human populations, and most likely already existed in ancestral hominids. Differences within our species are thus differences in fine-tuning of an existing mechanism. 

One can imagine the following scenario:

1. Initially, affective empathy existed primarily in women and served to facilitate the mother-child relationship.

2. Later, when human societies grew beyond the size of small kin groups, this mental trait took on a new task: regular interaction with people who were not necessarily close kin.

3. Selection thus increased the capacity for affective empathy in both sexes but more so in men.

4. This gene-culture evolution went the farthest in high-trust cultures.

Affective empathy and educational level in Mexico

To measure differences in affective empathy between human populations we can administer tests like "Pictures of Facial Affect" and the "Cambridge Behavior Scale." The first test is a measure of the ability to recognize emotion in human faces. The second test is a questionnaire with responses on a 4-point scale ranging from "strongly agree" to "strongly disagree."

In a recent study from Mexico these tests confirmed that affective empathy is stronger in women than in men. There were also differences by occupational status:

[...] we sought to explore facial emotion recognition abilities and empathy in administrative officers and security guards at a center for institutionalized juvenile offenders. One hundred twenty-two Mexican subjects, including both men and women, were recruited for the study. Sixty-three subjects were administrative officers, and 59 subjects were security guards at a juvenile detention center. Tasks included "Pictures of Facial Affect" and the "Cambridge Behavior Scale." The results showed that group and gender had an independent effect on emotion recognition abilities, with no significant interaction between the two variables. Specifically, administrative officers showed higher empathy than security guards. Moreover, women in general exhibited more empathy than men. (Quintero et al. 2018)

Why were the guards less able to recognize signs of distress or happiness on human faces? The authors offer no explanation but do note that the two groups differed in educational level: most of the administrative officers were university graduates, whereas the guards had gone no farther than middle school. 

In Mexico, educational level correlates with European admixture (Martinez-Marignac et al. 2007). Is this group difference in empathy really an ethnic difference?

The amygdala and political orientation in the U.S. and the U.K.

Tests are subjective and thus suffer from biases that may produce different results in different populations. To avoid this problem, a promising method is to measure the size or activity of brain structures that are associated with affective empathy. In the latest review of the literature, Tal Saban and Kirby (2019) assign the amygdala a key role:

Neuroscientists have identified the brain regions for the "empathy circuit": 1) the amygdala, responsible for regulating emotional learning and reading emotional expressions; 2) the anterior cingulate cortex (ACC), activated during observed or experienced pain in the self or others; and 3) the anterior insula (AI), which responds to one's pain and the pain of a loved one (Carr, Iacoboni, Dubeau, Mazziotta, & Lenzi, 2003). In recent years the mirror neuron system (MNS), comprised of the inferior frontal gyrus and inferior parietal cortex, has been suggested to also be involved in empathy (Gazzola et al., 2006, Kaplan and Iacoboni, 2006, Pfeifer et al., 2008, Baird et al., 2011). The broad notion that empathy involves "putting oneself in another's shoes" by simulating what others do, think, or feel, has been linked to the properties of mirror neurons.

The amygdala has been linked to affective empathy by MRI studies on healthy individuals and on individuals with amygdala lesions (Bzdok et al. 2012; Brunnlieb et al. 2013; Gu et al. 2010; Hurlemann et al. 2010; Leigh et al. 2013).

Two studies have found group differences in amygdala size or activity. When brain MRIs were done on 82 adults from the University of California at San Diego, the right amygdala showed more activity in Republicans than in Democrats (Schreiber et al., 2013). Similarly, a study of 90 adults from University College London found that the right amygdala was larger in self-described conservatives than in self-described liberals (Kanai et al., 2011).

Is affective empathy stronger in conservatives than in liberals? Or are these labels a proxy for something else? In both the United States and England, party politics is increasingly identity politics. While it is true that non-European minorities tend to be socially conservative, they nonetheless tend to be politically liberal, often overwhelmingly so. In the American study, party affiliation was undoubtedly the dimension being measured: participants were asked whether they were Democrat or Republican. This is less evident in the English study, where participants were asked about their "political orientation."

Both universities are ethnically diverse. University of California at San Diego is 36% Asian, 20% White, 19% non-resident alien, and 17% Latino (Anon 2019). There is no ethnic breakdown of University College students, but we know that a third of them come from outside the United Kingdom (Wikipedia 2019).


Brain MRIs provide a means to measure affective empathy objectively. We can thus evaluate differences between human populations, just as we have evaluated differences between men and women, and from individual to individual. This kind of comparative research will likely be done by accident rather than by design, as with the above three studies.

Another approach would be to identify alleles that correlate with a high level of affective empathy. A polygenic score could then be created, thus providing an objective yardstick for measuring this mental trait in any human population. Particularly promising are two polymorphisms. Alleles at the OXTR gene correlate with inter-individual differences in empathy, especially with affective empathy in women (Huetter et al. 2016). Alleles at the GNAS gene correlate with inter-individual differences in cognitive empathy, but only in women (Huetter et al. 2018).


Anon. (2019). University of California - San Diego, Ethnic Diversity.

Bzdok, D., L. Schilbach, K. Vogeley, et al. (2012). Parsing the neural correlates of moral cognition: ALE meta-analysis on morality, theory of mind, and empathy. Brain Structure and Function 217(4):783-796. 

Brunnlieb, C., T.F. Munte, C. Tempelmann, and M. Heldmann. (2013). Vasopressin modulates neural responses related to emotional stimuli in the right amygdala. Brain Research 1499:29-42. 

Gu, X., X. Liu, K.G. Guise, et al. (2010). Functional dissociation of the frontoinsular and anterior cingulate cortices in empathy for pain. Journal of Neuroscience 30:3739-3744. 

Huetter, F.K., H.S. Bachmann, A. Reinders, D. Siffert, P. Stelmach, D. Knop, et al. (2016). Association of a Common Oxytocin Receptor Gene Polymorphism with Self-Reported 'Empathic Concern' in a Large Population of Healthy Volunteers. PLoS ONE 11[7]:e0160059

Huetter, F.K, P.A. Horn, and W. Siffert. (2018). Sex-specific association of a common GNAS polymorphism with self-reported cognitive empathy in healthy volunteers. PLoS ONE 13(10): e0206114. 

Hurlemann, R., A. Patin, O.A. Onur, et al. (2010). Oxytocin enhances amygdala-dependent, socially reinforced learning and emotional empathy in humans. Journal of Neuroscience 30(14):4999-5007. 

Kanai, R., T. Feilden, C. Firth, and G. Rees. (2011). Political orientations are correlated with brain structure in young adults. Current Biology 21: 677 - 680.

Leigh, R., K. Oishi, J. Hsu, et al. (2013). Acute lesions that impair affective empathy. Brain 136(8):2539-2549.

Martinez-Marignac, V.L., A. Valladares, E. Cameron, A. Chan, A. Perera, R. Globus-Goldberg, N. Wacher, J. Kumate, P. McKeigue, D. O'Donnell, M.D. Shriver, M. Cruz, and E.J. Parra. (2007). Admixture in Mexico City: implications for admixture mapping of Type 2 diabetes genetic risk factors. Human Genetics 120(6): 807-819.

Melchers, M., C. Montag, M. Reuter, F.M. Spinath, and E. Hahn. (2016). How heritable is empathy? Differential effects of measurement and subcomponents. Motivation and Emotion 40(5): 720-730. 

Quintero, L.A.M., J. Muñoz-Delgado, J.C. Sánchez-Ferrer, A. Fresán, M. Brüne, and I. Arango de Montis.  (2018). Facial Emotion Recognition and Empathy in Employees at a Juvenile Detention Center. International Journal of Offender Therapy and Comparative Criminology 62(8) 2430-2446.

Schreiber, D., Fonzo, G., Simmons, A.N., Dawes, C.T., Flagan, T., et al. (2013). Red Brain, Blue Brain: Evaluative Processes Differ in Democrats and Republicans. PLoS ONE 8(2): e52970.

Tal Saban, M. and A. Kirby. (2019). Empathy, social relationship and co-occurrence in young adults with DCD. Human Movement Science 63: 62-72

Wikipedia (2019). University College London.


Anonymous said...

In his recent book, Robert Plomin seems to be disputing that "different parts of the brain do specific things and idea known as modularity". He says "generalist genes imply that individual differences in brain structure and function are largely caused by diffuse effects that affect many brain regions and functions".

Peter Frost said...

If that were true, why would lesions to specific brain regions have specific effects?

Anonymous said...