Empathy is defined as the ability to understand the feelings, emotions, and perspective of another person.  Empathy is critical for healthy social interactions, and impairments in empathy contribute to disorders of social interaction such as autism and psychopathy.

Women score higher on tests of empathy than men, leading researchers to examine a potential role for the male sex hormone testosterone in controlling empathy.  However, more recent studies have begun to explore the “dual hormone” hypothesis, that posits that testosterone interacts with the stress hormone cortisol to regulate social behaviours such as empathy.

A 2010 study by Jack van Honk and colleagues investigated the effects of acute testosterone administration on cognitive empathy in female volunteers. The study participants were administered either a placebo or a 0.5 mg dose of testosterone under the tongue, after which they took a test called, Reading the Mind in the Eyes Test (RMET).  This test measures how well an individual can interpret another’s emotions by reading expressions in the eye area of the face.

The participants took the test twice – once following administration of the placebo, and once after testosterone treatment – to assess how testosterone affected each subject individually.  Overall, the testosterone treatment reduced women’s scores on the RMET, suggesting that it impaired their ability to “read” the emotions and intentions of others through facial expressions in the eye area.

The researchers went one step further and measured the 2D:4D ratio of the study participants. This measure indicates the ratio in length between the index finger (second digit) and ring finger (fourth digit) and is considered a proxy measure of prenatal testosterone exposure.  Men have lower 2D:4D ratios than women, and women exposed to higher levels of testosterone in the womb display masculinized (lower) digit ratios. Elevated levels of foetal testosterone can occur in diseases such as congenital adrenal hyperplasia and polycystic ovary syndrome, and women with these disorders display reduced digit ratios. However, lower 2D:4D ratios are also found in otherwise healthy women due to individual variations in foetal hormone levels.

Van Honk et al. found that the RMET score reduction in response to testosterone was strongly correlated with the digit ratio, and that women with lower ratios (who thus had higher prenatal testosterone exposure) had stronger responses to testosterone.  These findings suggest an interesting “priming” effect of male hormone exposure during development that makes the brain more responsive to testosterone in adult life.

These findings provide support for the controversial ‘extreme male brain’ theory of autism, a disorder characterized by impairments in social interaction and a tendency to engage in repetitive behaviours. This theory posits that autism represents an extreme version of the normal male brain profile that is characterized by an increased systematizing ability and a reduced empathizing ability in comparison to females. The pathological impairment of empathy in autism may therefore arise from excessive “male” hormone levels during development.  Accordingly, reduced 2D:4D ratios have been observed in autistic individuals and in their first-degree relatives.

While this and other studies have demonstrated a clear inhibitory effect of testosterone on cognitive empathy, they tell only one part of the story. Other hormones may also play a role in the regulation of empathy.

One such hormone is cortisol, the body’s main stress hormone.  Cortisol and testosterone form the key players in the “dual-hormone hypothesis,” that seeks to explain how empathy, aggression, dominance, and other social behaviours are controlled by the brain.

A study by Zilioli et al. examined whether the levels of testosterone and cortisol in the blood were associated with empathy in a group of university students. The students took a series of tests that included the RMET as well as the Interpersonal Reactivity Index (IRI), a questionnaire designed to measure different aspects of empathy.  Saliva was collected for the analysis of cortisol and testosterone, and associations between hormone levels and RMET and IRI scores were assessed.

As predicted, testosterone levels were higher in men, and women scored higher on tests of empathy.  In women, there were no associations between hormone levels and empathy scores. However, an interesting association emerged between testosterone, cortisol and empathy in men, where an interaction between testosterone and cortisol was detected in relation to men’s IRI scores.

In men with higher than average testosterone levels, low cortisol predicted low empathy scores, whereas high cortisol predicted high empathy scores.  This association was not observed for men with testosterone levels below the mean, in whom cortisol showed no association with empathy.

In women, a similar pattern emerged when they were grouped according to testosterone levels: women with low cortisol and high testosterone had reduced empathy scores.  However, these differences did not meet the cut-off for statistical significance, probably due to the smaller number of women than men in the study.

A high testosterone, low cortisol profile has been linked with competitiveness and aggressive behaviour.  This profile has also been associated with psychopathy, a mental condition defined by anti-sociality, egotism, and impaired empathy.

In contrast, men with high testosterone levels and high cortisol in this study displayed increased empathy.  What are the implications for real life behaviour?

The researchers suggest that this profile could underlie certain altruistic behaviours such as acts of heroism where public safety is concerned.  They also posit that elevated cortisol levels might replicate a state of mild internal stress, which might be helpful for turning on feelings of empathy.

References

van Honk J, Schutter DJ, Bos PA, Kruijt AW, Lentjes EG, Baron-Cohen S (2011) Testosterone administration impairs cognitive empathy in women  depending on second-to-fourth digit ratio. Proc Natl Acad Sci USA. 108(8):3448-52. doi: 10.1073/pnas.1011891108

Peterson E, Miller SF (2012) The Eyes Test as a Measure of Individual Differences: How much of the Variance Reflects Verbal IQ? Front Psychol. 3:220. doi: 10.3389/fpsyg.2012.00220. eCollection 2012.

Baron-Cohen S (2002) The extreme male brain theory of autism. Trends Cogn Sci. 6(6):248-254. DOI: dx.doi.org/10.1016/S1364-6613(02)01904-6

Zilioli, S., Ponzi, D., Henry, A. et al. (2015) Testosterone, Cortisol and Empathy: Evidence for the Dual-Hormone Hypothesis. Adaptive Human Behavior and Physiology 1: 421. doi:10.1007/s40750-014-0017-x

Image via skeeze / Pixabay.