Under Pressure: How Personality Developed as a Response to Social Pressures in Early Societies

by Chandler Brown English

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What makes us who we are? On the simplest level, one could say physical features like hair or eyes make us unique. However, these are expressions of our genetic make-up, of which we share 98.8% with chimps. Common practice is not to judge a book by its cover, but by its contents. Personality, and its resulting behaviors, are our contents. With increased brain size, humans also developed more sophisticated regions of the frontal cortex, which are associated with executive functions like personality expression, social cognition, decision making, and moderating social behavior. Personality also affects reproductive success within various populations. This essay proposes that these same social forces influence the development of personality in humans. Rather than personality being the result of a gene variation expressed across a species, the writer argues that personality is a behavioral adaptation to environmental pressures of increasing social complexity.


It has been known that primates have larger brains and greater cognitive abilities than other animals, making them capable of using more complex tools, identifying faces, and possessing theory of mind (Boesch & Boesch, 1993; Premack & Woodruff, 1978; Parr, Winslow, Hopkins, & Waal, 2000). Neocortex volume has been shown to be positively correlated with group size (Dunbar, 1992). This trend coincides with findings from animal personality studies. Avian evidence shows promising support for this indirectly (Öst et al., 2015). Similarities in personality development in humans and primates have been found (Weiss & King, 2014). Duckworth (2010) found that “limitations to behavioral flexibility due to time, energetic, or functional constraints can lead to individual specialization” (p. 752). This in turn supports the idea that individual specialization is possible as a result of social pressures. Buss (1991) and Nettle (2006) both identify that personality traits play a key role in the evolution of personality in humans. Utilizing the existing scientific evidence, this philosophical discussion will explore the meaning of personality and attempt to examine how it may have first arisen.

I believe personality is a behavioral adaptation to environmental pressures of increasing social complexity. As our brains grew, becoming larger and more complex due to social complexity (Dunbar, 1992), I propose there came a point (T_0) where humans started utilizing the structures associated with personality expression in response to social complexity (G_0). From T_0 onward, humans developed and adapted their ability to express personality in response to social complexity, and through genetics, transferred these changes to subsequent generations (G_1, G_2, G_3, etc.). To demonstrate this idea important parameters and an operationalized definition of personality must be established first. Next, a brief discussion of the role that the brain plays in personality will follow. Then, existing findings of personality research of various animals will be analyzed, including comparative analyses of research involving human and non-human primates. Finally, using evidence from human personality research and its role in natural selection, I explain how personality might be a behavioral adaptation to environmental pressures of increasing social complexity.

1. Defining Personality and Important Parameters

First we must operationalize our definition of personality. According to the Encyclopedia of Psychology, personality is the “individual differences in characteristic patterns of thinking, feeling and behaving” (Kazdin, 2000). Beekman and Jordan (2017) define animal personality through two concepts: 1) the actions are consistent “behavioral response(s) across time and concept” (p. 618) and 2) the expressions of these behaviors correspond with other behaviors (Beekman and Jordan, 2017, p. 618). For the duration of this paper, I will define personality as follows: individual differences in characteristic patterns of behavior (i.e. thinking, feeling, acting, and responding to stimuli) that are consistent across time and setting. This embodies both definitions and takes into account the nuance specificities, while also making it generalizable to include all animals, including humans.

Additionally, there are a few important parameters to keep in mind. First, I acknowledge and accept the biological foundations of personality and the role genetics play in the transfer of personality from generation to generation. However, this paper investigates the role that environment of early humans had in catalyzing personality expression, specifically the role of social complexity; all discussion of the specific biological mechanisms of expression and transmission of personality is to be understood as occurring after T_0.

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2. Brain Size and The Structures of Personality

Dunbar (1992) argued that primates have larger brains and greater cognitive abilities than other animals, and that this greater cognitive ability is a result of primates’ larger brains. At the same time, Dunbar (1992) found a relationship between population size and the ratio of neocortex to body size. Social complexity, in turn, requires the brain to work harder in social situations, resulting in a larger, more complex neocortex (Dunbar, 1992). Prior to Dunbar’s 1992 publication, three general explanations for why primates had a larger neocortex than other species had been proposed. These explanations, ranging from the ecological importance of cognitive skills in primates to the role of maternal nutrients, emphasized that larger neocortex of primates allowed for greater social structure and complexity. Dunbar argued against these explanations because he felt the causation arrows were pointing in the wrong direction. Rather, he felt that it was the social complexity that increased the neocortex sizes (1992). When describing his 1992 findings, Dunbar said “it seems that it is the correlation between neocortex ratio and group size that seems to be responsible for the apparent relationship between these ecological variables and neocortex size” (p. 479). By dispelling the ecological causes for neocortex size, Dunbar’s results suggested that there are other possible ways for group size to influence the brain of primates (1992). The subfield of social primatology has drawn inspiration from Dunbar’s pivotal research and only furthered its validity (Brosnan et al., 2009; Weiss & King, 2014).

In addition to size, specific brain structures within the neocortex also play a role in personality expression. DeYoung et al. (2010) and Latzman et al. (2014) both published studies involving brain structures and personality in human and non-human primates. De Young et al. (2010) found that “extraversion covaried with volume of medial orbitofrontal cortex” and “conscientiousness covaried with volume in lateral prefrontal cortex” (p. 280). Meanwhile, neuroticism and agreeableness covaried with brain regions associated with “threat, punishment, and negative affect” and the basics of Theory of Mind, respectively (p. 280). Additional studies demonstrated that the PFC’s role in regulating personality and emotion (Etkin, Egner, & Kalisch, 2011; Koenigs, 2012; Ochsner & Gross, 2005), as well as the role that the medial frontal cortex (MFC) and anterior cingulate cortex (ACC) play in social cognition (Amodio & Frith, 2006). Altogether, this literature supports the idea that overall brain size, including the size of specific brain regions, plays a role in personality expression. If social complexity is shown and accepted to be positively correlated with brain size and the sophistication of specific brain structures involved in personality expression are associated with their relative size, then social complexity indirectly drives the complexity of personality expression through relative brain size. Existing evidence from animal studies support this conclusion.

3. Brain & Personality Expression in Nature

Neurological research of personality within animals only began recently. In a review of existing literature, Penke, Denissen, & Miller (2007) found evidence of “environmental heterogeneity favoring personalities exists” for some non-human species (p. 564). Nettle (2006) analyzed the literature on “behavioral strategies” and “genetic polymorphism” in other species to establish implications for the maintenance of personality variation in humans. Nettle made two generalizations: “variation is a normal… result of the fluctuations in nature of selection,” and “behavioral alternatives can be considered as trade-off” (2006, p. 625). Duckworth (2010) proposed that on non-human personality evolution argues that behavior is flexible and this conclusion is supported significantly by the behavioral attributes, like imprinting. But a more recent study researching avian personality and breeding experience showed “no clear pattern in the correlations between social tendency and personality traits” (Öst et al., 2015, p. 170). Evidence like this highlights the idea that although many animals may exhibit personality traits, they often lack the executive function capabilities to use them effectively or consistently.

The field of behavioral ecology has also contributed to advancing animal personality research. Dall and Griffith (2014) emphasized two principles to guide studying ecology and personality variation. First, within particular species, “personality variations, [when viewed as] behavioral traits, are likely to be most ecologically relevant,” and second, frame the experiment in a way that adequately includes the important variation in “repeatability within and amongst individuals” (Dall and Griffith, 2014, p. 1). Beekman and Jordan (2017) argued that the degree of variation seen in animal behavior could come from different factors, and this argument is supported by evidence from a number of species of fish and social insects. Male African cichlid form social hierarchies based on the “relative social position and relationships to other individuals in the social network,” exhibiting both behavioral and physiological differences (Beekman and Jordan, 2017, p. 621). Studies of assorted marine life have also demonstrated how changes in environmental context affect the “fitness outcomes associated with particular phenotypes” (Nettle, 2006, p. 628). Scheiner (1993) found mate selection based on reaction norms are very common and “very important” when investigating “the evolution of caste systems in social insects,” citing instances where single ant hives or nests contain multiple sub-castes of worker ants who are not genetically differentiated into their castes. Rather they are differentiated “by rearing condition… a form of phenotypic plasticity” (Scheiner, 1993, p. 35). The effects of the ecology of an area varies based on the stability. If the area is stable, behavioral variation exists on the “population level but not at an individual level” (Beekman and Jordan, 2017, p. 619). However, instability results in behavioral variation at the individual level. This is demonstrated by how when “a hungry individual continues to be successful in obtaining food, it will maintain a high-energy levels” (Beekman and Jordan, 2017, p. 619). Beekman and Jordan (2017) support the 2010 argument of Dingemanse, et al. that “the trait of interest” is “an organism’s behavioral response over an environmental gradient [or] ‘context’” (p. 619). Both Beekman and Jordan (2017) and Dingemanse, et al. (2010) use “the term behavioral reaction norm to describe the set of behavioral phenotypes that a single individual produces in environmental contexts” (Beekman and Jordan, 2017, p. 619). Researchers have drawn a direct link from “behavioral reaction norms to phenotypic plasticity,” and, as Beekman and Jordan pointed out, this is “an important driving force in adaptive evolution” (Dingemanse, et al., 2010; Beekman and Jordan, 2017, p. 620). Some of these changes can occur within a species’s lifetime, potentially allowing for a behavioral plasticity adaption or acclimation to take place as a limited “trial-and-error learning” style (Penke, Denissen, & Miller, 2007, p. 569). Phenotypic plasticity is limited because there is a chance a trial could result in death or an irreversible change.

These normative behavioral reactions to instability within an area is ample support for the generalizability of the argument of this paper. It is this instability resulting in individual changes that I believe strongly support my argument. Johnstone and Manica (2011) showed in humans that during times of instability, leadership within groups increased as conflict and overall volatility of the group decreased. That is, groups seek order in times of chaos. Therefore, I conclude that personality is present within different animal groups to varying degrees, and these variations can be accounted for by the social complexity of the species and thus correlate with the average neocortex size of each species. More importantly, I believe the evidence presented by the findings suggest that origin of personality is not genetic, because if this were the case, we would most likely only find evidence of personality in animals that are significantly similar to humans on a genetic level. While this counterargument that the genetic component to personality is older than expected is not inconceivable, I believe it devalues the extensive knowledge we have about animal personalities while ignoring findings which correlate size of structure and scale of functionality (i.e., Dunbar 1992).

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4. Personality Similarities Between Human and Non-Human Primates.

Primates not only are humans’ closest relatives, but they also exist in similar social groups. DeYoung et al. (2010) and Latzman et al. (2014) both published studies involving brain structures and personality. De Young et al. (2010) found that while neuroticism and agreeableness covaried with generally associative brain regions, “extraversion covaried with volume of medial orbitofrontal cortex” and “conscientiousness covaried with volume in lateral prefrontal cortex” (p. 820). The specific brain structures mentioned in this study are all housed within the PFC. This is critical when considering the findings of Latzman et al. (2014) on personality in chimpanzees (2014). Latzman et al. found that many of the “chimpanzees rated as higher on Openness and Extraversion had greater… volumes in the anterior cingulate cortex (ACC)” and those rated higher in “dominance had larger… volumes” in the left ACC and right PFC (2014, p. 63). While these studies are not a one-to-one comparison, the findings suggest that personality is not only not a human specific quality but that it is also testable and measurable in other species.

Studies of the personality similarities between human and non-human primates show great promise. Weiss and King (2014) studied “age and sex differences in the chimpanzee and orangutan personality domains Extraversion, Dominance, Neuroticism, and Agreeableness” (p. 648). Weiss and King (2014) found “significant interactions” indicating that, relative to females, over time, male chimpanzees “maintained high levels of Activity, a facet of Extraversion, and Dominance” and generally scored in higher Neuroticism than females (p. 649). These interactions were not found in male orangutans (Weiss & King, 2014). Weiss and King’s research “suggest that gene–culture coevolution shape personality development, and suggest that sex differences have evolved independently in different species” (2014, p. 648). To ensure their findings would be more accurately comparable to humans, Weiss and King (2014) only studied “apes 12 years or older [or] approximately humans age 18 or older” and measured “the relationship between age and personality scores using the correlations between both the ungrouped age variable and the within-species” (p. 652). This gene-culture coevolution may seem contradictory to my argument, but it should be reiterated my argument is that personality originated as a behavioral adaptation to environmental pressures of increasing social complexity. Weiss and King’s (2014) research regarded development within the individual across a species, not within a species over time. Most importantly for this paper, their study found that human and chimpanzee personality development are similar, both characterized by “individuals becoming more introverted, less competitive, and less emotional and having greater behavioral controls” (Weiss & King, 2014, p. 658). Because chimps are our closest living relative, this finding opens the door to further research that investigates the origin of personality. Brosnan et al. (2009) emphasized the importance of interdisciplinary work when combining primatology and personality research, arguing that by including primate research methods in the field of social psychology, this may “shed light” in areas that have not been frequently focused, as well as possibly untangling “unexpected or inconsistent date” (p. 142). Overall, the findings in non-human primate social research further the idea that personality is universal and varies based on the animal’s upper level cognitive capabilities. These upper level cognitive capabilities, as explained by Dunbar (1993), coincide with social complexity.

5. Human Personalities, Natural Selection, And Sexual Selection

The origins of human personality and the role they play in human evolution is a complex discussion and can be discussed in many ways. One way to analyze human personality is through the Five Factor Model (FFM). Nettle (2006) argued that there are “benefit-cost… trade-offs” between Big-Five personality traits and population diversity (p. 622). I believe this is evidence for personality having a positive or neutral effect on reproduction; there are few, extreme cases where personality traits are extreme enough to be negative.

Studies on the relationship between genes and personality have brought promising results to the nature versus nurture debate over personality. However, while these results explain persistence of personality, they do not explain the origin. Bouchard and Loehlin state that while “personality traits… have distal causes,” ultimately “proximal internal and external stimuli” influence when and what personality traits are exhibited (2001, p. 244). This would suggest that personality traits have external and internal motivators that influence when and what traits are expressed (Bouchard and Loehlin, 2001). The authors noted identifying the latter was particularly tricky because it required them to answer the following question: what differentiates internal stimuli motivating personality expression and external factors influencing an internal response that motivates personality expression? I would argue that the differentiation from an evolutionary stand-point is irrelevant. For instance, when a dramatic temperature change occurred, early agriculturalists would begin gathering and storing food in preparation (Hildebrand et al., 2016). Their sense of urgency caused by the weather was more complex than feeling a cold breeze and in response gathering food. At a point in time, they learned to adapt to changes in the weather, even predicting changes in seasons. However, prior to that level of cognitive advancement, something else had to motivate organisms to begin adjusting to weather. I believe the piece Bouchard and Loehlin are missing is the psychological concept of cognitive dissonance.

Cognitive dissonance is the mental discomfort that occurs when there are contradictions between a person’s actions and thoughts (Festinger, 1962). In this context, it can be viewed as the discomfort occurring when one’s behavior and thoughts contradict. Before the idea of storing food was passed down from generation to generation, there had to have been a point when humans realized that the colder weather required preparation. While I partially agree that this is the same primal instinct experienced by other animals when the weather changes, I believe that when it was expressed in early humans, this was also the earliest form of cognitive dissonance. This concept applies to personality as well as behavior. Cognitive dissonance caused by cold weather causes the individual to begin exhibiting thriftiness and caution. This can be viewed as a form of survival instincts. Recall how Johnstone and Manica (2011) argued that in humans, during times of instability, leadership within the group increased as overall volatility of the group decreased. Those who possessed the leadership traits were more likely to express them in settings where leadership was more easily enacted, and I believe this hierarchy would remain in place until the group saw change was necessary. Although rudimentary, this is the earliest form of politics, as too many leaders in one area would create either factions within the group or a reduction in the number of leaders of the group (i.e. killing off competing leadership). This is a reflection of Beekman and Jordan’s (2017) aforementioned finding that environmental instability results in variation at the individual level, not the population level. This is also supported by a study by Grabo, Spisak, and Vugt (2017) looking into the evolutionary importance of charisma, in which they present an example of how, from an evolutionary viewpoint, a personality trait can shape a population and its structure.

Personality has been found to play a role in not only reproduction but also reproductive success. Alvergne and colleagues (2010) found that personality dimensions can be used to “predict reproductive success differently between men and women” (p. 11748). Similarly, Hill and Kintigh theorized in a 2009 study that better hunters were more reproductively successful. First, the ability to hunt was crucial for survival, and those who were the best at it would possess the social power to have first picks at a mate. Secondary factors that contributed to one’s ability to hunt well also played a role. The ability to hunt quietly was important, as a noisy hunter could scare away prey and potentially attract other predators. This would result in more evolutionarily beneficial traits being passed on through natural selection.

Existing evidence from evolutionary personality psychology furthers our understanding of how the environment can influence human personalities, thus contributing to our discussion of phenotypic plasticity. Buss (1991) emphasized the importance of a given situation when assessing the psychological and behavioral strategies used by humans as solutions to environmental condition problems. These environmental conditions can result in genetic changes within a population. For instance, in resource-rich, or “luxuriant,” environments, where childhood survival is less dependent on paternal support, selection favors “a personality more prone to sexual promiscuity and intrasexual competition” (Penke, Denissen, & Miller, 2007, p. 567). These findings by Penke, Denissen, & Miller (2007) are due to an increased frequency of the more risk-seeking allele 7R occurring at allele locus DRD4. But on the same gene, when resource-scarcity occurs, these attributes are not favored as they are disadvantageous in such conditions (Penke, Denissen, & Miller, 2007; Harpending & Cochran, 2002). This is an example of how environmental conditions can result in an individual acclimating to conditions within their lifetime, while also influencing future genetic variation within a population.

Cognitive dissonance only explains how pro-survival personality traits, or behavioral instincts, arose but fails to account for non-survival traits related to personality, like artistic creativity. To explain how non-survival traits arose, I point to the factors that resulted in the Renaissance. In the simplest way, a burst of ideology and art began when individuals had the intellectual resources and the time to use them. In this sense, when a group of early humans had grown large enough and developed basic social structure and complexity where not all individuals within the group were actively participating in food gathering at all times, some members would not be hunting. This would result essentially in free time for individuals, who could not hunt or were bad at it, and they would find a way to make themselves useful in other ways, through art, storytelling, and other creative ventures. In addition to having more time available for other endeavors, as Dunbar’s 1992 study showed, this increased social structure and complexity would also continue to increase the size of the neocortex over time. Abilities and traits like this would be unnecessary and evolutionarily disadvantageous if the group were not able to support themselves. These unique, individually distinguishable traits, or personality traits, made individuals within a species seem more desirable. Until the social structure became complex enough to require individuality to achieve a mate, only survival traits, like the ability to hunt, were necessary. Around this time, along with this social complexity, social niches began to form (Penke, Denissen, & Miller, 2007; Buss, 1991). Segal and Macdonald (1998) state that “variation in [human] personality may constitute a range of viable strategies matching the opportunities available in the complex niche environment of human societies” (p. 159). In the same way a town grows, as a group of people grow, greater complexity is required to maintain order and the needs of the people. This idea is also directly supported by Dunbar’s findings involving social complexity.


There is a counter-possibility that personality was the result of biological forces (i.e. personality resulting from increased genetic variation over time, expressed more or differently with each divergent iteration). Nettle (2006) argued the population already contains an abundance of genetic variation, citing strong evidence that “the combination of trade-off and genetic polymorphism” seem to be an effective approach to explaining the heritable basis of personality (p. 622). But even Nettle noted that this does not address how it arose initially, and in doing so, also failed to establish a point origin, or T_0 (2006).

At the same time, evidence of the power and resilience of genetics over the environment does exist. To briefly venture off topic, twin studies, like Segal (2017), have found similarities in “abilities and personalities despite the extreme differences in their rearing circumstances” (p. 1). However, these are studies comparing effects that environmental differences have on the personalities of present day genetically identical humans, only looking at the personality differences between two humans from a particular generation (G_n) at a particular time (T_n). While twin studies are fascinating and demonstrate how powerful genetics can be in general, they fail to take into account how the relative brain size affects personality expression between species or how that personality expression has changed between generations. These are two key components to consider. Even within species, genetics seem like an unrealistic explanation for personality differences between generations over time; rather, I would argue that social environment is a more sound explanation for large, intergenerational personality changes.

To illustrate this in a more modern context, take, for example, that in 2009, Barack Obama, an African American male, became the 44th president of the United States. Now, recall that we defined personality as the individual differences in characteristic patterns of behavior (i.e. thinking, feeling, acting, and responding to stimuli) that are consistent across time and setting) and consider that the human germline mutation rate is approximately 0.5×10−9 per base pair per year (Scally, 2016). Only slightly more than 2.5×10−8, or .000000022, base pair mutations have occurred since two white men were acquitted for murdering a 14-year old African American, Emmit Till, after he allegedly whistled at a white woman 50 years ago. I find it hard to believe that in 50 years this large-scale change in the personality of many individuals within a nation are the result of genetic change, in any of its many forms, alone. Rather, environmental factors were the primary influence on the development of personality but continue to influence and change personality alongside genetics.

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I have proposed that personality resulted as a behavioral adaptation to environmental pressures that were developed in response to increasing social forces and social complexity. The findings from the field of behavioral genetics support that genes do play a role in how personality persists and spreads from generation to generation. However, this area lacks solid evidence of a catalyst for the emergence of personality existing across species. Meanwhile Dunbar’s (1992) groundbreaking study on the relationship between group and neocortex size support a potential origin for personality. As mean group size increased, so did the ratio of the neocortex to the rest of the brain. The neocortex is the “‘thinking’ part of the brain” and it seems “plausible to use neocortical volume as the main index of cognitive capacity” as it is involved in higher order thinking (Dunbar, 1992, p. 473). Knowing that humans have the largest neocortex ratio and personality is a component of the executive functions that occur in this region, it is not unreasonable to make the leap that humans have a more complex personality network than other species. This might explain the gaps in personality research involving other animals. Existing research and literature on primate and non-primates’ personality show similar patterns of behavioral response and personality development with each other, as well as with humans. This demonstrates how much more universal personality is than originally thought. One factor contributing to the individual responses to environmental pressures is the concept of cognitive dissonance. This form of psychological discomfort could logically explain why personalities began being expressed in early humans. Additionally, increased social complexity allowed for individuals to begin participating in non-survival activities, such as creative pursuits, which are arguably an expression of personality that would have not been necessary prior to this social structure.

Future Research and Closing Thoughts

The old debate that humans are the only animals with personality has since been debunked, but research on the complexity of personalities in non-humans has not been studied enough. As Trillmich & Hudson (2011) and others have said, further research in animal personality research is needed. One approach to future research would be studying the social complexity and neocortex ratios of animals relative to their personality complexity. This would build off of Dunbar’s (1992) research, further investigating the influence of social complexity on neocortex size, and, in turn, personality complexity.

Further research on human personalities may also be useful. Cross-cultural research, like that of Allik and McCrae (2004), may shed some light on the origins of personality in respect to culture. Researching the social complexities of interpersonal groups in various cultures and societies may also be useful, especially research on social structures of non-WEIRD societies (WEIRD meaning Western, Educated, Industrialized, Rich, Democratic). One way to test this idea on humans, would be to have several groups of individuals, who have tested to having very similar Big Five personality trait scores, be placed in a situation in which they interact to accomplish tasks (or survive) and testing how their personality scores change after being in isolation with others that are very similar. Having these individuals spend time together, doing various cooperative tasks, and then testing to see if their personalities change due to over-exposure to those similar to themselves could demonstrate the how and when behind the divergence of personality between G_0 and G_1. If this shows to be effective, conducting a similar study with chimpanzees, or other animals, could also be enlightening.

While gathering evidence for this paper, I began noticing the critical role phenotypic plasticity played across species in behavior and the further implications of this concept in species, specifically humans, as environmental factors become more social in nature. In order to coexist with others, we must exist in Durkheimian solidarity with each other to increase both survival rates and quality of life. So while living in complete isolation is possible, it is not sustainable for any sexually reproducing species, as reproduction will not occur. Thus group living is not only beneficial for the current generation of a species but also beneficial to insure the occurrence of future generations. This idea is further demonstrated by the specific Durkheimian concept of organic solidarity, where individuals “must depend on other people in the community for their survival,” arguing “that such societies are held together by their interdependency, and by their shared belief” or collective conscience (Kretchmar, 2013). As social structure becomes more complex, group norms and beliefs becomes more important for individual success within social groups, which in turn becomes part of homeostasis. Humans attempt to maintain homeostasis through an environmental-biological feedback loop. We can use the information that we receive to govern our behavior as well as how we express emotions and thoughts based on how we interpret social situations. This is known as social cognition (Amodio & Frith, 2006). Combining the ideas of phenotypic plasticity and this feedback loop, it would seem that at least humans possess the capability to receive feedback and modify behavior or personality expression based on the information received. Drawing inspiration from the foundations of Ecological Rationality, once feedback from the environment is received, I believe an individual can make “fast and frugal” decisions by matching the current situation of environments to preexisting heuristics (Gigerenzer & Todd, 1999; Todd & Brighton, 2016).

One way of doing this is by utilizing one’s “adaptive toolbox… that include fast and frugal heuristics, quick shortcuts, and rough rules of thumb,” allowing the individual to “exploit the structure of the environment” (Todd & Brighton, 2016, p. 11). While some of these tools are “learned through individual experience or through cultural inheritance,” Todd and Brighton (2016) believe some are also “pre-wired for us by evolution” (p. 12). Thinking of this adaptive toolbox as containing both decision-making tools, as well as one’s personality traits and summative capital (as described by Bourdieu, 1986), this toolbox can be used to navigate, comprehend, and effectively respond to environmental feedback in attempt to maintain equilibrium.

A microeconomics supply and demand (S&D) model can be constructed to visualize these changes in expression in response to the feedback information, where the x-axis is the value placed on a particular factor and the y-axis is the relative quantity expressed. In this model, the supply curve is the relative character trait expression (expression of behavioral traits, personality, values, etc.) of an individual within a particular environmental area, like social space or social group. The demand curve is the relative levels of characteristic traits desired by, or acceptable to, those within the social space or social group, or their collective conscience, that provides the feedback to the individual. Like in a regular S&D curve, both curves fluctuate and adjust, sliding along one another in response to each other, and also shift completely in attempt to find equilibrium (OpenStax, 2015). Similar to a traditional micro model, the factors that would shift a the S & D curves as a whole have analogous scenarios. For example, a rightward/increasing shift in the supply curve would occur when there is a price of inputs for production decreases, or an decreased cost of utilizing personal capital. Likewise, an example of when a leftward/decreasing shift would occur in the demand curve if overall population tastes decrease within the market for, or when the market’s reception of the individual decreases. In this proposed theoretical model, the individual is the product/supply and the social space is the consumer/demand, creating an economy of character.


Amodio, D. M., & Frith, C. D. (2006). Meeting of minds: the medial frontal cortex and social cognition. Nature Reviews Neuroscience, 7(4), 268-277.

Allik, J., & Mccrae, R. R. (2004). Toward a geography of personality traits. Journal of Cross-Cultural Psychology, 35(1), 13-28.

Alvergne, A., Jokela, M., & Lummaa, V. (2010). Personality and reproductive success in a high-fertility human population. Proceedings of the National Academy of Sciences, 107(26), 11745-11750.

American Museum of Natural History. (n.d.). DNA: Comparing humans and chimps. Retrieved November 09, 2017, from https://www.amnh.org/exhibitions/permanent-exhibitions/human-origins-and-cultural-halls/anne-and-bernard-spitzer-hall-of-human-origins/understanding-our-past/dna-comparing-humans-and-chimps/

Beekman, M., & Jordan, L. A. (2017). Does the field of animal personality provide any new insights for behavioral ecology? Behavioral Ecology, 28(3), 617-623.

Boesch, C., & Boesch, H. (1993). Diversity of tool use and tool-making in wild chimpanzees: Discussion. Use of Tools by Human and Non-Human Primates. British Library Document Supply Centre Inside Serials & Conference Proceedings. Clarendon, Oxford. 158-168.

Boissy, A. (1995). Fear and fearfulness in animals. The Quarterly Review of Biology, 70(2), 165-191.

Brosnan, S. F., Newton-Fisher, N. E., & Vugt, M. V. (2009). A melding of the minds: When primatology meets personality and social psychology. Personality and Social Psychology Review, 13(2), 129-147.

Buss, D. M. (1991). Evolutionary personality psychology. Annual Review of Psychology, 42, 459-491.

Clark, A. B. & Ehlinger, T. J. (1987). Pattern and adaptation in individual behavioral differences. Perspectives in Ethology (Bateson, P. P. G. & Klopfer, P. H., eds). Plenum, New York, 1-47

Dall, S. R., & Griffith, S. C. (2014). An empiricist guide to animal personality variation in ecology and evolution. Frontiers in Ecology and Evolution, 2. doi:10.3389/fevo.2014.00003/full

DeYoung, C. G., Hirsh, J. B., Shane, M. S., Papademetris, X., Rajeevan, N., & Gray, J. R. (2010). Testing predictions from personality neuroscience: Brain structure and the big five. Psychological Science, 21(6), 820-828.

Dingemanse, N. J., Kazem, A. N., Wright, J., & Reale, D. (2010). Behavioural reaction norms: animal personality meets individual plasticity. Trends in Ecology & Evolution, 25(2), 81-89.

Dingemanse, N., & Réale, D. (2005). Natural selection and animal personality. Behaviour, 142(9/10), 1159-1184.

Duckworth, R. A. (2010). Evolution of personality: Developmental constraints on behavioral flexibility. The Auk: A Quarterly Journal of Ornithology, 127(4), 752-758.

Dunbar, R. (1992). Neocortex size as a constraint on group size in primates. Journal of Human Evolution, 22(6), 469-493.

Etkin, A., Egner, T., & Kalisch, R. (2011). Emotional processing in anterior cingulate and medial prefrontal cortex. Trends in Cognitive Sciences, 15(2), 85-93.

Festinger, L. (1962). Cognitive dissonance. Scientific American, 207(4), 93-106.

Grabo, A., Spisak, B. R., & Vugt, M. V. (2017). Charisma as signal: An evolutionary perspective on charismatic leadership. The Leadership Quarterly, 28(4), 473-485.

Guthrie, J. F. (2017). Integrating behavioral economics into nutrition education research and practice. Journal Of Nutrition Education And Behavior, 49(8), 700-705.

Harpending, H., & Cochran, G. (2002). In our genes. Proceedings of the National Academy of Sciences of the United States of America, 99(1), 10-12.

Hill, K., & Kintigh, K. (2009). Can anthropologists distinguish good and poor hunters? Implications for hunting hypotheses, sharing conventions, and cultural transmission. Current Anthropology, 50(3), 369-377.

Johnstone, R. A., & Manica, A. (2011). Evolution of personality differences in leadership. Proceedings of the National Academy of Sciences, 108(20), 8373-8378.

Kazdin, A. E. (2000). Encyclopedia of Psychology. Washington, D.C.: American Psychological Association.

Koenigs, M. (2012). The role of prefrontal cortex in psychopathy. Reviews in the Neurosciences, 23(3), 253-262.

Kretchmar, J. (2013). Durkheim’s mechanical and organic solidarity. Research Starters: Sociology (Online Edition).

Latzman, R. D., Hecht, L. K., Freeman, H. D., Schapiro, S. J., & Hopkins, W. D. (2015). Neuroanatomical correlates of personality in chimpanzees (Pan troglodytes): Associations between personality and frontal cortex. NeuroImage, 123, 63-71.

Nettle, D. (2006). The evolution of personality variation in humans and other animals. American Psychologist, 61(6), 622-631.

Ochsner, K., & Gross, J. (2005). The cognitive control of emotion. Trends in Cognitive Sciences, 9(5), 242-249.

Öst, M., Seltmann, M. W., & Jaatinen, K. (2015). Personality, body condition and breeding experience drive sociality in a facultatively social bird. Animal Behaviour, 100, 166-173.

Parr L. A., Winslow J. T., Hopkins W. D., de Waal F. B. M. Recognizing facial cues: Individual discrimination by chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta (2000). Journal of Comparative Psychology, 114(1), 47-60.

Penke, L., Denissen, J. J., & Miller, G. F. (2007). The evolutionary genetics of personality. European Journal of Personality, 21, 549-587.

Premack, D., & Woodruff, G. (1978). Does the chimpanzee have a theory of mind? Behavioral and Brain Sciences, 1(4), 515-526.

Scally, A. (2016). The mutation rate in human evolution and demographic inference. Current Opinion in Genetics & Development, 41 (Genetics of human origin), 36-43.

Scheiner, S. (1993). Genetics and evolution of phenotypic plasticity. Annual Review of Ecology and Systematics, 24, 35-68.

Segal, N., & Macdonald, K. (1998). Behavioral genetics and evolutionary psychology: Unified perspective on personality research. Human Biology, 70(2), 159-184.

Segal, N. (2017). Twins reared together and apart: The science behind the fascination. Proceedings of the American Philosophical Society, 161(1), 1-17.

Sih, A., Bell, A. & Johnson, J. C. (2004a). Behavioral syndromes: an ecological and evolutionary overview. Trends in Ecology & Evolution, 19(7): 372-378.

Sih, A., Bell, A. M., Johnson, J. C. & Ziemba, R. E. (2004b). Behavioural syndromes: an integrative overview. The Quarterly Review of Biology, 79(3): 241-277.

Todd, P. M., & Brighton, H. (2016). Building the theory of ecological rationality. Minds and Machines, 26(1-2), 9-30.

Trillmich, F., & Hudson, R. (2011). The emergence of personality in animals: The need for a developmental approach. Developmental Psychobiology, 53(6), 505-509.

Weiss, A., & King, J. E. (2015). Great ape origins of personality maturation and sex differences: A study of orangutans and chimpanzees. Journal of Personality and Social Psychology, 108(4), 648-664.

Wilson, D. S., Clark, A. B., Coleman, K. & Dearstyne, T. (1994). Shyness and boldness in humans and other animals. Trends in Ecology & Evolution, 9(11), 442-446.

Author’s Note: Originally written during the Fall of 2017 for the course Anth 4790: Human Adaptation under the instruction of Dr. Susan Tanner Ph.D. and graduate student Christina Lee, this paper has since been revised and repurposed for journal submissions. Please address comments and concerns regarding this paper to Chandler Brown English at chandler.brown.english@gmail.com.

Acknowledgments: This paper is dedicated to all the teachers that told me I’d never amount to nothing, the lost, broken, or voiceless, my cat Dirty Randi, and all the people in the struggle. I would like to thank all of the people who taught me to love learning and inspired me to never stop trying, as well as all of my friends and family for putting up with me throughout all these years, and Tom Morello.

Lastly, a very special thank you to the five pairs of eyes and countless sets of ears that helped refine this paper, and encourage anyone, from any field of study or line of work, with thoughts or feedback to do the same. Interdisciplinary and multicultural collaboration are key to developing well-rounded ideas and theories, and allowing problems to be addressed from many angles and points of view. Together, we are stronger.

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