Does Regional Temperature Affect Personality?
Regional temperature may have a "Goldilocks effect" on personality development.
Posted Nov 26, 2018
Human personality traits are known to systematically differ across geographical regions around the world. Although there are all sorts of reasons why this might be, a new study found that regional ambient temperature was a significant factor (Wei et al., 2017). More specifically, people growing up in regions with more clement ambient temperatures (closer to 22 °C/about 72 °F) had higher levels of extraversion, emotional stability, agreeableness, conscientiousness, and openness to experience compared to those who grew up in regions with either colder or hotter temperatures. Regional temperature might affect one’s personality development through factors like temperature-related fatigue. It could be that certain personality traits might be more adaptive in colder or hotter environments. On the other hand, personality development might be subject to a “Goldilocks effect”: clement environments might be beneficial, whereas too hot or too cold surroundings might take their toll.
For humans, the ambient temperature that is most optimal for personal comfort is usually about 22 °C/72 °F. Environments that markedly deviate from this tend to be considered either too hot or too cold. The authors of a new study (Wei et al., 2017) suggested that ambient temperature clemency (i.e. how close the temperature is to 22 °C/72 °F) might be an important factor affecting the development of personality traits, particularly during one’s formative years. This is because when the temperature is mild, people might be more willing to venture outdoors and have new experiences, e.g. socializing and exploring their environment. On the other hand, when it’s too cold or hot, people might be more inclined to stay indoors and explore their environment less. To test, this the authors conducted studies in two geographically large yet culturally distinct countries, China and the USA. In the Chinese part of the study, over 5000 students from 59 cities participated. To rule out reverse causality, that is, that people might migrate to cities that reflect their personalities, the study only included people who had spent their childhood in their birthplace. Additionally, to rule out the possibility that participants’ parents might have migrated to certain cities that suited their personalities and then passed their traits onto their children, participants were limited to those who were born in their ancestral home region. For each city, they calculated a clemency index by determining the difference between the city’s average annual temperature for the previous forty years and 22 °C/72 °F. That is, cities closer to this temperature were considered more clement, whereas those that were much hotter or colder were less clement. As expected, they found that personality traits were associated with temperature clemency, that is, greater clemency was associated with higher levels of each of the Big Five traits of extraversion, emotional stability (i.e. lower neuroticism), agreeableness, conscientiousness, and openness to experience. This held true even after accounting for a variety of other variables that might affect personality, such as GDP per capita, population density, age, gender, and – intriguingly – influenza incidence. This last variable is worth commenting on, as personality traits were also associated with influenza incidence, significantly for emotional stability, conscientiousness, and openness to experience (although there were marginal trends for extraversion and agreeableness). Some personality theorists argue that the Big Five traits can be subsumed into two higher order factors called stability (a combination of emotional stability, conscientiousness, and agreeableness) and plasticity (a combination of extraversion and openness to experience). As expected, greater temperature clemency was also associated with higher levels of both stability and plasticity.
To replicate the Chinese findings in the USA, the authors examined regional ambient temperatures at the zip-code level with a very large sample (over 1.6 million people) who provided information about their personality traits and hometown in an online survey. As with the Chinese sample, was associated with higher levels of extraversion, emotional stability, agreeableness, conscientiousness, and openness to experience, as well as stability and plasticity. Again, these associations held even after controlling for other factors that might influence the association, including age, gender, education, population density, and GDP per capita. Interestingly, temperature clemency seemed to have larger effects on personality traits in China than in the USA, while GDP per capita generally seemed to have larger effects in the USA than China. The US sample had no data for influenza, so this could not be compared.
The authors of this study argued that temperature is likely to affect personality development through environmental exploration. It might also be worth considering the effects of temperature clemency on personal well-being. All of the Big Five traits are associated with subjective well-being in various ways (Steel, Schmidt, & Shultz, 2008). For example, positive affect (pleasant feelings, such as enthusiastic, active, and alert) is strongly associated with extraversion, and to a lesser extent with the other traits, while negative affect (feelings of subjective distress) is strongly associated with neuroticism. There is evidence that personality and subjective well-being may each affect each other. That is, not only can personality can affect one’s level of well-being, but well-being may, over the long-term, have effects on one’s personality. One study that followed the same people over four years, found that not only do personality traits influence changes in one’s level of subjective well-being over time but that one’s initial level of subjective well-being leads to changes in one’s personality as well (Soto, 2015). Specifically, people with higher initial extraversion, agreeableness, and conscientiousness and lower neuroticism at the onset of the study experienced increases in subjective well-being (i.e. higher satisfaction with life and positive affect, and lower negative affect) by the end. On the other hand, people with initially high levels of subjective well-being experienced increases in agreeableness and conscientiousness and decreases in neuroticism and (surprisingly) extraversion.
There is also evidence that temperature clemency has some effect on subjective well-being, although the findings are somewhat complex. One study of American adults found that temperatures above 21 ºC/70 ºF were associated with reduced well-being, i.e. decreased positive affect, and increased negative affect and fatigue, while colder temperatures (below 20 ºF) actually tended to increase well-being (Noelke et al., 2016). Similarly, a study in Japan found that hotter temperatures were associated with decreased happiness (Tsutsui, 2013). Notably, the temperature range during the period of the study was 5 ºC to 30 ºC, which meant that participants experienced fairly mild winters but uncomfortably hot summers. On the other hand, a study in Estonia examined well-being within a colder temperature range, about –15 ºC to 18 ºC. Interestingly, warmer temperatures were associated with slight increases in both negative and positive affect. That is, compared to colder temperatures, people experienced more intense emotions, both positive and negative, as the weather became warmer. On the other hand, colder temperatures were associated with increased feelings of fatigue. Putting these findings together suggests that inclement temperatures can have adverse effects on mood (i.e. positive and negative affect), although the effects seem more consistent for hotter than colder temperatures. Additionally, both very hot and very cold weather can increase feelings of fatigue. Perhaps, temperature might influence personality development through its effects on well-being, especially fatigue. That is, fatigue might inhibit certain aspects of one’s personality development. Admittedly, the effects of temperature on well-being seem to be small, and effects on the well-being of children, let alone their personality development, have not been studied, so this is highly speculative.
Another question that arises from the study by Wei et al. is whether variations in personality traits related to temperature are adaptive in an evolutionary sense (i.e. they help people survive better) or a maladaptive side-effect of living in a harsher environment? There is a theory that personality variation has evolved in humans and other animals because, for any given personality trait, there is no optimal level of that trait that is adaptive in every environment (Penke, Denissen, & Miller, 2007). Hence, high or low levels of certain traits might be better suited to certain environments. In support of this, one study found that in countries with high historic levels of a variety of infectious diseases, people had lower average levels of extraversion and openness to experience (Schaller & Murray, 2008). This might be adaptive because people who are highly extraverted seek out more social contacts and are more sexually adventurous, which could increase their risk of exposure to disease in certain environments. Similarly, people high in openness to experience like to seek out novel things and to challenge social norms. However, certain social norms might exist to protect people against infectious diseases, e.g., norms for food preparation and hygiene, and avoidance of unfamiliar foods and water sources. In low disease risk environments, high openness to experience may lead to beneficial new discoveries, but in high-risk environments, being too open to new experiences might be hazardous. On the other hand, it is possible that reductions in certain traits might be an adverse consequence of disease prevalence. For example, exposure to disease might increase one’s propensity to anxiety and depression, which are related to high neuroticism or reduce one’s overall competence, resulting in low conscientiousness. I find it interesting in this regard that Wei et al. found that influenza prevalence in China was associated with lower levels of certain traits, such as openness to experience, conscientiousness, and emotional stability, and to a lesser extent extraversion, and agreeableness. independently of temperature. It’s possible that this might reflect a combination of adaptive and maladaptive responses to this disease. Hence, being low in openness to experience in a high influenza prevalence environment might have a protective effect by encouraging adherence to traditional methods of disease prevention, insofar as these are effective. On the other hand, reduced conscientiousness and emotional stability (i.e. high neuroticism) might be maladaptive outcomes of influenza prevalence. Similarly for ambient temperature, it is possible that certain traits might be an adaptive response to inclement weather, e.g. being more introverted might be adaptive in cold environments. On the other hand, the trait of conscientiousness might seem even more adaptive in difficult (e.g. inclement) environments than more comfortable ones. In this vein, I noted in a previous post that people living in poorer countries with shorter average life expectancies tend to have higher average levels of conscientiousness than people in richer countries, even though at an individual level, people high in conscientiousness tend to have better health and to live longer. I considered that this might be an adaptation to living in harsher environments where there are more threats to life. However, for temperature, this does not seem to apply. This might be because people feel more fatigued in very hot or very cold climates, which might reduce their ability to behave conscientiously. This might apply to other traits, such as agreeableness and emotional stability, which are mostly associated with positive personal outcomes, such as improved relationships and better mental health. The study by Noelke et al. found that there were no differences in the effects of heat on well-being between areas with either mild or hot summers, even when the annual average temperature was the same, suggesting that people do not become adapted to extreme heat. This might suggest that clement ambient temperatures are also beneficial for personality development, whereas overly hot or cold environments may have a detrimental effect, and that reduced levels of big five traits in these environments might not be particularly adaptive.
 For the statistically minded, the p-values for these two traits were < .10.
Noelke, C., McGovern, M., Corsi, D. J., Jimenez, M. P., Stern, A., Wing, I. S., & Berkman, L. (2016). Increasing ambient temperature reduces emotional well-being. Environmental Research, 151, 124–129. https://doi.org/10.1016/j.envres.2016.06.045
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Wei, W., Lu, J. G., Galinsky, A. D., Wu, H., Gosling, S. D., Rentfrow, P. J., … Wang, L. (2017). Regional ambient temperature is associated with human personality. Nature Human Behaviour, 1(12), 890–895. https://doi.org/10.1038/s41562-017-0240-0