The Role of Personality in Mating
It’s not unusual to encounter a couple and note how different the two are from each other. On the extreme end, we have the HBO show Curb Your Enthusiasm. The neurotic and disagreeable Larry David—whose catchphrase whenever he does something inappropriate is “what—no good?”—couldn’t be more different than his emotionally stable wife Cheryl. Yet, somehow, they made it work (for the most part—and yes, we are aware it’s just a TV show). In humans, you’ll find all sorts of interesting combinations of personality traits. Personality variation is a major component of mating intelligence. Together with intelligence and creativity, personality plays a critical role during courtship by signaling traits that men and women consider important in a mating partner. Many even rate dispositional variables (e.g., intelligence, creativity, humor, personality) as more important than situational variables (e.g., wealth, social status) or physical attractiveness in selecting a mate.1
An evolutionary perspective allows us to look at different combinations of personality traits. We can see how they cluster in evolutionarily predictable ways, how they may have been differentially related to reproductive success among our distant ancestors, and how they play out in today’s mating marketplace. For instance, although we normally think of emotionally stable, agreeable, and conscientious people as “well adjusted,” the evolutionary perspective allows us to stand back and ask, well adjusted for what?
In the last chapter, we argued that the display of cognitive abilities such as artistic creativity and humor is sexy, at least in part, because they reveal an individual’s total load of rare, mildly harmful deleterious mutations. Evolution is constantly trying to keep up with new genetic variants introduced through mutation. When selection cannot keep up and remove all of the variants, it is not able to optimize a trait. Because complex traits like intelligence and creativity are the result of many interacting genes (i.e., polygenic), it is particularly difficult for selection to keep up with all the new variants in personality, so differences remain in the general population.
As we hinted at in the prior chapter, many forms of creativity are sexy not just because of the cognitive abilities they signal but also because of the personality traits they are broadcasting. For instance, when the cellist Jacqueline Du Pré played the Elgar Concerto with the Philadelphia Orchestra, she was displaying her intelligence and creativity as well as her dispositions for expressiveness, kindness, tenderness, and compassion. According to mating intelligence, both cognitive displays and personality dispositions play a role in courtship display. However, from an evolutionary genetics perspective, we think about cognitive abilities a bit differently from personality.
When it comes to the development of cognitive abilities, a low mutation load will always be beneficial, regardless of the environment. In contrast, the reproductive consequences of having various personality traits are more dependent on environmental conditions. For instance, high levels of extraversion may be more conducive to reproductive fitness in unstable environments where exploration is crucial, whereas the other end of the spectrum—introversion—may be more conducive to reproductive success in stable environmental conditions.
The fact that environments have varied so much throughout the course of human evolution means evolution was not able to find one single optimal trait conducive to reproductive fitness across all contexts. Increasingly, evolutionary psychologists agree that individual differences in personality traits are best conceptualized from this mating trade-offs perspective.2
The fact remains that people only have limited time and energy, so there will be trade-offs for any mating strategy. Here are some common trade-offs involved in human mating faced across our species and, for some of them, even across other species3:
• Should you spend time attracting new mates or invest all your time and energy in the one you’re with?
• How much time and energy should you invest in detecting mating-relevant threats, such as cues that your mate is cheating or has lost interest, status, resources, or health?
• How patient should you be regarding future mating opportunities? Because life is finite and uncertain, how much should you weigh your current reproductive opportunities against future opportunities or costs?
• How much empathy should you have for significant others? What’s the best balance to strike between caring about the well-being of significant others versus being opportunistic and caring about your own immediate advantage?
• How much time and energy should you invest in developing courtship displays? It takes a lot of time and effort to develop social-valued skills and then become creative and productive in those skills enough to attract a wide range of potential mates.
From an evolutionary perspective, there is no absolute answer to each trade-off. Because physical and cultural ecological conditions varied quite a bit during the course of human evolution, it makes sense that human mating strategies would also be variable. Every culture, and every person within that culture, must strike its own right balance for each of these mating trade-offs. And each culture does.
Owing to such trade-offs, the most likely candidate mechanism for maintaining personality differences in the human population is balancing selection. Balancing selection only works on traits that are balanced in the sense that both extremes of the same trait are conducive to reproductive success to the same degree depending on the environment. To take our earlier example, extraversion would be a good candidate for balancing selection if high levels of extraversion were conducive to fitness in certain environments and low levels of extraversion were equally as conducive to fitness in other environments.
This delicate balancing act can happen in a number of different ways, but the best candidate for how this works with personality traits is through a process called negative frequency-dependent selection.4 This balancing act typically occurs in social environments (as opposed to just focusing on the physical environment) and only selects genes that are rare in frequency.5 This type of selection is particularly relevant to human personality, which is particularly social in nature and involves many genes that are differentially conducive to reproductive fitness depending on the social environment and situations in which the genetic variants are rare in any one particular context. Bottom line: you cannot understand the existence of differences in personality without taking into account the social context.
In this chapter, we adopt this mating trade-offs approach and link personality to the mating intelligence framework. Before we take a look at the direct relationship between personality and mating outcomes, let’s start by looking at how personality traits are intimately intertwined with other behaviors to form a person’s mating strategy. Although personality is an important courtship display for mating intelligence, it is part of a larger system that evolved for specific survival and reproductive purposes.
According to the life history perspective,6 a wide range of traits and behaviors—from self-control and personality to attachment style, reproductive strategies, growth, longevity, and fertility—cluster together in evolutionarily predictable ways and represent different mating strategies that were adaptive for reproductive success among our very distant ancestors. Even today, these ancestral genes play a role in certain contexts.
Areas that are more safe and stable (such as many reasonably high socioeconomic suburban areas) are more conducive to holding resources and long-term planning. In these areas, you find that people tend to be physically larger (because they have the time and energy to invest in health); focus on offspring quality instead of quantity; have delayed sexual development, lower fertility, higher interbirth intervals, higher parental investment, lower infant mortality, and greater longevity; and have more intense competition for scarce resources. They also tend to take fewer risks, are less impulsive, and are more likely to follow group norms and have high group cohesion. Entire species, such as elephants, exhibit this pattern of development because in the ecologies in which they evolved, these long-term strategies paid off. These species are referred to as K-selected species.
Areas that are more harsh and unpredictable, however, tend to be more conducive to a short-term, impulsive strategy. In these areas, you find that the people tend to be physically smaller; focus on offspring quantity rather than quality; have early and fast sexual development, higher fertility, and lower longevity; and have little competition for scarce resources. They also tend to take more risks, are more impulsive, are less likely to follow externally imposed rules of conduct, and have lower group cohesion. Entire classes of animals, such as rabbits, exhibit this pattern of development because in the ecologies in which they evolved, these short-term strategies paid off. These species are referred to as r-selected species.
Human ecologies differ quite a bit from each other. Consider the Canela people of Brazil. The women of Canela pursue a short-term mating strategy (in the parlance of evolutionary psychology, they are “sexually unrestricted”). They have public ceremonies at which women are encouraged to have sex with multiple partners. Men in this society support this behavior and must hide their jealousy. They certainly don’t give women derogatory labels for their promiscuous behavior. Why are things the way they are in Canela society?
Life history theory lends a cue here. Canela society is a matrilineal society (resources are passed along the female lineage), the environment is unpredictable, resources are scarce, and males experience high rates of mortality. When a women finds out she is pregnant, she engages in extramarital affairs with high-status men to confuse paternal certainty. As a result, none of the men can ever be assured he is the father of the child. This guarantees that the surviving men will invest in the child and not kill, abuse, or neglect the child because it could be theirs. This is a much smarter strategy on the female’s part than relying on assistance from one mate who is likely to die early. This situation results in several men investing in or protecting their children.7 If Canela women do get married, the couple is expected to remain married until all their children are adults. Additionally, the husband is expected to tolerate his wife’s affairs, and the general attitude among members of Canela society is that the welfare and survival of children is more important than a man’s control over a women’s sexuality.8 The characteristics of Canela society, including high levels of sexual promiscuity, uncertainty about future resources, and high rates of mortality, suggest that the people of Canela have shifted their life history strategy closer to the r-selected side because of their ecological conditions.
This example of a matrilineal, harsh, unpredictable, and resource-poor society was used to illustrate the extreme end of the fast-slow life spectrum. It turns out that humans cross the entire spectrum, from fast to slow and everywhere in between (compare North American New England suburbia to the Canela society, for instance!). This is because all of the crucial environmental dimensions (matrilineal vs. patrilineal, resource rich vs. resource poor, unpredictable vs. stable, harsh vs. safe) can vary independently of the others.
For instance, resource scarcity, by itself, has the opposite effect of a harsh and unpredictable environment and is more conducive to living the slower life. When resources are scarce, it is important to use long-term planning skills to save what you’ve got and conserve valuable energy and calories. In fact, resource-poor but safe ecologies are relatively stable, monogamous, and equitable in terms of contributions from both parents. In these societies, it makes more sense for a pair to settle down and work together to invest in the long-term survival of their children. It is to neither partner’s benefit to mate with many different partners under these circumstances. In these societies, people actually have a fair chance of being rewarded for their long-term investment in resources.9
During the course of human evolution, natural and sexual selection sculpted and coordinated various traits to make sure they did not strategically interfere with one another. For example, risky, impulsive attempts at mating effort (i.e., seduction) may interfere with the careful, long-term planning that is beneficial for survival and long-term pair bonding. As a result, evolution selected various psychological traits to cluster together in adaptively coordinated ways. These clusters were selected and sculpted by evolution to maximize reproductive fitness within particular environments.
Because those living life in the fast lane tend to focus on short-term gains at the expense of long-term costs, their core adaptive psychological traits should involve rebelliousness, risky behaviors, impulsivity, and a focus on mate quantity and reduced parental investment. On the contrary, because those living a slower life focus on the long-term, their core adaptive psychological traits should involve careful risk considerations, a preference for monogamy, high parental investment, and conformity of social rules. Note that when we say “should” here (and throughout this book), we mean “can be expected to, from an evolutionary perspective.” We are not in the business here of telling anyone how they should act in life.
The evidence suggests that personality traits do cluster in just these ways among humans. A. J. Figueredo and colleagues10 administered a wide range of indicators of life history strategy to 222 psychology undergraduates. All of these indicators were reasonably correlated with each other, forming an overarching “K-factor.”
Those scoring higher on this K-factor (i.e., those living a slower life) tended to report feeling higher levels of emotional closeness as a child toward a father figure (e.g., “I want to be like my biological father”), higher levels of security in adult romantic attachment (e.g., “I do not often worry about being abandoned”), lower levels of mating effort (e.g., “I would rather date one boy at a time than several boys at once”), lower levels of Machiavellianism (e.g., “I tend to trust people”), and lower levels of risk-taking attitudes and behaviors (e.g., “I wouldn’t approach someone very attractive if I thought it were a long shot”). Those scoring higher on the K-factor also tended to report lower levels of neuroticism and psychoticism, and there was nearly a positive association with extraversion.
Further research revealed that this K-factor does have a heritable basis. Analyzing a nationally representative sample of 309 identical twins and 333 fraternal twin pairs aged 25 to 74 years, Figueredo and colleagues11 looked at 30 scales of life history traits (e.g., quality of family relationships, altruistic behaviors), medical symptoms (e.g., thyroid disease, ulcer), personality traits (e.g., neuroticism, extraversion, conscientiousness, openness to experience), and social background (e.g., financial status). They found that all the items were moderately related to each other and that people scoring higher on this over-arching K-factor tended to live a slower life, whereas those scoring lower on the K-factor tend to live a faster life. This higher-order K-factor explained most of the genetic correlations among the scales, was 68% heritable, and accounted for 82% of the genetic differences among the lower-order factors. According to the researchers, these results suggest that life history strategy may be influenced by a large number of genes that coordinate the activation of a wide array of traits. Regulatory genes don’t just activate themselves, though—they require environmental triggers, or else they won’t be expressed. What are the important environmental triggers?
Barbara Brumbach, Jose Figueredo, and Bruce Ellis12 found that two environmental factors in particular explained a considerable amount of the differences found in life history strategy among thousands of adolescents followed up from youth to young adulthood (see Chapter 5 for other environmental conditions that can influence a person’s mating strategy). Both environmental harshness (“self-reported exposure to violence from conspecifics”) and unpredictability (“frequent changes or ongoing inconsistency in several dimensions of childhood environments”) independently explained a large part of the differences in a K-factor consisting of an intertwined number of life history traits such as mental and physical health, relationship stability, sexual restrictiveness, social deviance, and economic success. Life history traits in adolescence were fairly stable across time and were significantly related to life history strategy in young adults. According to the researchers,
… by the time people reach their mid-twenties, they have formed a coherent life history strategy that is characterized by their overall health, approach to romantic and sexual partners, and the amount of effort they have put into education and employment.
This research suggests that the interaction of nature and nurture exerts its most potent effects during youth. The unpredictability of the environment can take many forms, but a particularly important contributor to the development of a person’s life history strategy is his or her early family environment. Let’s take a look at those familial influences.
Although it is certainly true that human parental investment is extremely high compared with other species,13 there are many circumstances in which children are raised in unpredictable family environments with little parental care. Various studies, including those that have controlled for the effects of genetic transmission, show that stressful parent-child relationships and negative parenting have a significant effect on pubertal timing. This effect seems to be strongest for females, although family stress can accelerate adrenarche (a stress hormone) in males as well.14 There is also research on the effects of total parental absence on the development of life history strategy. In general, when fathers don’t invest in parental care, there is a tendency for boys to live the fast life—increased delinquency, aggression, and other indicators of high mating effort.15
In a large review of the literature, Bruce Ellis16 presented evidence that girls who grow up in a home where the father is absent or negligent in their parenting are more likely to go through their first menstrual cycle (i.e., “menarche”) by the age of 12 years and, compared with their peers, to show increased fertility, greater levels of manipulative and exploitative attitudes, greater risk-taking behavior, higher incidence of affective disorders, social aggression, sexual promiscuity, preference for sexual variety, lower adult attachment to romantic partners, and less parental care devoted to one’s offspring. In fact, the age in which “father-absent girls” tend to go through menarche is related to the number of years of father absence, the amount of time fathers spent taking care of daughters during the first five years of life, and the amount of affection observed in parent-child relationships.
Framing the effects of parental absence on life history strategy in an evolutionary context, Belsky and associates17 and Chisholm18 argue that children in the first few years of life use their level of family stress, unharmonious parent-child relationships, father absence, and marital conflict as cues of risk and uncertainty, which then influences the development of their reproductive strategy.
A safe and predictable environment (neighborhood, social, and parental) will tend to trigger a slower reproductive strategy, with a focus on later reproduction, high parenting effort, longer-term couple relationships, and more secure, trusting, mutually beneficial close relationships. A dangerous and uncertain environment, on the other hand, will tend to trigger the fast life, involving earlier reproduction and physical maturation, higher mating effort, less parental investment, a higher incidence of short-term and uncommitted relationships with partners, and increased opportunism and risk-taking.
Insecurely attached adults do report shorter estimates of their own life expectancy,19 so there does appear to be a link between adult attachment security and perceptions of the harshness of the environment.
Building on the work of Belsky and associates20 and Chisholm,21 Marco Del Giudice22 has shed light on the developmental time course leading from infant attachment styles to mature, sexually differentiated strategies. Del Giudice proposes that life history strategies develop in a flexible, multistage fashion.
According to this view, life history strategies remain open to continual modification depending on life stage and context (although some people may be more flexibly adaptive than others). Del Giudice also proposes that throughout human development, there are developmental switch points when an individual’s genes are calibrated with information from the environment, and this integration then shapes an individual’s choice of life history strategy.23
The complex, dynamic interplay between nature and nurture is mutually reinforcing. People’s genes, which are partially shared with their parents, may influence to a certain extent what aspects of the environment they engage in, and those environments can in turn trigger and reinforce the expression of those genes. This can be unfortunate in situations in which, for example, the genes that predispose someone to living the fast life cause that person to take dangerous risks that make his or her environment even more dangerous, causing a dangerous cycle. Therefore, when looking at the development of life history strategy, neither the environment nor genetic make-up can be viewed in total isolation.24
Cutting-edge research in evolutionary biology is addressing issues central to child development, such as plasticity and genotype-by-environment interactions (GxE).25 The study of organismic development is even becoming a major foundation of the new theoretical synthesis in evolution.26 The field of developmental evolutionary psychology has much promise for shedding light on data that may not have made sense before, such as why attachment patterns correlate with such a wide range of developmental outcomes as aggression, sexuality, cooperation, and psychopathology.27
For example, recent epigenetic research looking at genotype-by-environment (GxE) interactions suggests that not all people may be equally influenced by environmental conditions; some girls and boys may be more reactive to stressful early environments than others because their highly reactive and negatively emotional temperament may be more affected by parenting than that of other children.28 Indeed, revisions of Belsky and associates’29 and Chisholm’s30 models put these genetic effects back into the picture. This doesn’t mean, however, that all people can’t use a wide range of cues to adjust their life history strategy. Most people can, and do.
This mutually reinforcing pattern of nature and nurture assures that neither the genes nor the environment alone is destiny. Just because your life history strategy at a certain age is rather stable does not mean you can’t change your strategy (if you so desire); life history strategies are plastic and highly sensitive to environmental triggers (although this doesn’t mean change is necessarily going to be easy): change the triggers, and you increase the chances that you will change the pattern of gene activations. Evolution “designed” humans to be highly sensitive to environmental cues and built in a great deal of plasticity into the human genome. Such plasticity would be more adaptive than rigidly “hard-wiring” at birth a person’s life history strategy or allowing the environment to exert complete control. As Figueredo and colleagues31 point out, evolution would favor developmental plasticity to allow for a wide range of possible environments.
The bottom line is that humans are extremely flexible strategically when it comes to mating because the adaptive value of different mating tactics depends on the ecology of the individual. What is an adaptive mating tactic in one society may be considered counterproductive in another. Every society has to solve reproductive trade-offs, such as whether to spend time investing in mating effort or to spend time and energy investing in parenting, in their own way. Different ecologies call for different ways of solving the unique reproductive trade-offs people face.
This strategic flexibility means that evolution was never able to settle on a stable solution and optimize any particular mating function in humans, allowing for individual differences to remain. So far, we discussed the broader picture of clusters of personality traits and how they tie in with a variety of other life history variables. Now it’s time to focus solely on the major personality dimensions, starting at the broadest level of personality description.
Personality psychologists have agreed on five main personality dimensions that people differ on (dubbed the “Big Five”): extraversion, neuroticism, agreeableness, conscientiousness, and openness to experience.32 Before we dive into the reproductive consequences of each of these factors individually, we will stand above the Big Five for a moment and look at two “meta-traits” that account for much of the shared variance among the lower-order dimensions.33 We will be looking at these meta-traits with an eye toward implications for reproductive success.
The first meta-trait can be referred to as stability and is a blend of emotional stability (low neuroticism), conscientiousness, and agreeableness. This factor is all about self-control. Those who score high in stability have a need to maintain a sense of order in their lives. To help them accomplish this goal, they restrain themselves from engaging in a wide variety of behaviors. Individual differences in stability have been linked to the serotonergic neuromodulator. Serotonin has regulatory or inhibiting effects on mood, behavior, and cognition. Serotonin helps increase a person’s vigilance while also reducing the negative affect that might get in the way of a person’s effort to control the environment. One research study found that the association between serotonin and impulse control was the most consistent association found between serotonin and personality.34
The second meta-trait can be referred to as plasticity and is a blend of extra-version and openness to experience. High scorers on plasticity have a drive to engage in the world, and they soak up novelty from the environment like a sponge. Differences in plasticity have been linked to functioning of the dopaminergic neurotransmitter system. Dopamine can have activating effects on behavior and cognition and is linked to approach behavior, sensitivity to rewards, and breadth of thinking. Dopamine has shown linkages to positive affect, broad thinking, and mental flexibility.
It is possible for any one person to have any combination of these two meta-traits; stability and plasticity are not opposites. The opposite of plasticity is rigidity, and the opposite of stability is instability. What are the implications of each meta-trait for reproductive success? To provide clues, let’s take a deeper look at how people scoring on each dimension tend to act in the real world.
Jacob Hirsh, Colin DeYoung, and Jordan Peterson35 measured the two meta-traits in a community sample of 307 participants. Personalities were rated both by participants and three of their friends. Participants were given 400 behaviors and were asked to check off which ones they frequently engage in.
Those scoring higher on the stability meta-trait tended to engage less in a wide variety of behaviors. Of all the significant relations with stability (82), 90% were negative. Here’s a sampling of the top 10 behaviors people high in stability tended to avoid:
1. Tried to stop using alcohol or other drugs
2. Drank alcohol or used other drugs to make myself feel better
3. Swore around other people
4. Hung up the phone on a friend or relative during an argument
5. Lost my temper
6. Spent an hour at a time daydreaming
7. Yelled at a stranger
8. Rode a motorcycle
9. Awakened in the middle of the night and was unable to get back to sleep
10. Became intoxicated
These behaviors cluster together to enable self-control and long-term gains and would therefore be potentially conducive to a long-term reproductive strategy. Indeed, one of the most consistent findings in the literature is that both men and women report wanting high levels of agreeableness, conscientiousness, and emotional stability in a long-term mate.36 Of course, this makes sense—these are all traits that are conducive to bonding and mutual satisfaction.
Not only do people desire these traits in a mate, but they also tend to seek mates who are somewhat higher than themselves in terms of their own perceived mate value in levels of extraversion, agreeableness, conscientiousness, and emotional stability.37 People apparently want to feel as though they “acquired” a partner of higher quality than themselves. This situation leads people during courtship to hide their own levels of neuroticism and exaggerate their levels of emotional stability, conscientiousness, and agreeableness.38 In turn, women, perhaps because of their higher biological cost of mating, report being skeptical about such displays.39
In a recent study, Portia Dyrenforth, Deborah Kashy, Brent Donnellan, and Richard Lucas40 looked at the personality predictors of relationship and life satisfaction in three very large, nationally representative samples of married couples in Australia, the United Kingdom, and Germany. They looked at three different effects: actor effects, which refer to the association between a person’s personality and their own satisfaction; partner effects, which refer to the association between a person’s personality and his or her partner’s satisfaction; and similarity effects, which refer to the association between the similarity of both partners and each partner’s satisfaction.
They found that actor effects on relationship and life satisfaction were large, and partner effects were small, but still substantial. Taking actor and partner effects into account, similarity effects were minimal. The three best personality predictors (what they refer to as the “Big Three”) for both actor and partner effects were agreeableness, conscientiousness, and emotional stability. These findings provide further support for the notion that the meta-trait of stability is well suited to meaningful, long-lasting relationships and life satisfaction. The higher your level of stability, the higher the likelihood that you will be satisfied in your relationship and in life, and the higher the likelihood that your partner will be satisfied. The research also suggests that your own level of stability does a better job of predicting relationship and life satisfaction regardless of your partner’s similarity.
What about plasticity? Whereas those scoring high in stability tended to avoid engaging in a lot of behaviors, those scoring high on the meta-trait plasticity tended to engage in a wide variety of behaviors. Here’s a sampling of behaviors people high in plasticity tend to engage in:
1. Was consulted for help or advice by someone with a personal problem
2. Planned a party
3. Attended a public lecture
4. Told a joke
5. Gave a prepared talk or public recital (vocal, instrumental, etc.)
6. Spent an hour at a time daydreaming
7. Wrote a thank you note
8. Wrote a love letter
9. Attended a city council meeting
10. Entertained six or more people
Actually, one of the behaviors on the list not included here might just be our favorite—perhaps the one most conducive to reproductive success: Lounged around my house without any clothes on! Anyway, you get the idea. All of these behaviors involve an active exploration and engagement in the world. As can be seen by the previous list, the plasticity dimension can manifest in a number of ways and may facilitate a fast life history strategy. People who engage in the world may increase their opportunities for short-term mating in a number of ways. By being more proactive, they may increase their overall chances by just approaching more people. Also, by being more inclined to display their creativity and abilities, their personality traits might acts as “amplifiers” that increase their chances of being noticed, and as we saw in Chapter 2, creative displays are highly valued in a potential mate. Also, people may be attracted to those high in plasticity (especially for a short-term encounter) because of their outgoing, “exciting personalities.”41
Therefore, at the broadest level of description it seems as though differences in human personality reflect restraint and engagement. Stability is associated with avoiding engaging in potentially disruptive impulses, whereas plasticity is associated with engaging with the world, creatively and socially. The former may be more conducive to a long-term mating strategy, whereas the latter may be more conducive to a short-term mating strategy.
In short, there are advantages and disadvantages of each profile for reproductive success; it depends on your mating goals. Also, just because you tend to display one profile over another does not mean you can’t change your behavioral patterns. Change your patterns of behavior and context, and your neurotransmitters will change as a result. Because a wide range of behaviors tend to cluster together to form a particular evolutionary adaptive strategy, to make a change requires formulating higher-order rules. These can take the form: “I want to like to like engaging,” or “I want to want to be more stable,” or even “I want to like to be more stable and engage more in the world.” Or whatever is consistent with your goals.
The meta-trait framework explains a lot of personality differences, but it does not explain everything. Even in Hirsh’s study,42 the researchers found that each of the Big Five traits offered unique prediction of behaviors. Also, recent research in the emerging field of personality neuroscience43 suggests that each trait of the Big Five (except for the openness/intellect domain) is associated with the volume of different brain regions.44
In one study, the researchers found among 116 healthy adults, extraversion was associated with volume in the medial orbitofrontal cortex (a region involved in reward); neuroticism was associated with reduced volume in a number of brain regions typically associated with threat, punishment, and negative affect; agreeableness was related to reduced volume in various regions involved in theory of mind; and conscientiousness was related positively to volume in the middle frontal gyrus in the lateral prefrontal cortex, a region involved in self-regulation, planning, and self-control. Note that these gray-matter correlations are not fixed—volume in different areas of the brain changes constantly throughout the life span as a person accumulates experiences.
Each of the Big Five dimensions has important implications for reproductive success. Building on the work of MacDonald, Nettle has argued that variations in each of the Big Five dimensions can be conceptualized as variations in mating strategies that had different reproductive consequences under different environmental conditions in our ancestral past.45 Let’s now put each of the Big Five traits in the spotlight (they’ve been waiting very patiently!) and see how each one relates to reproductive outcomes.
Emotional stability, agreeableness, and conscientiousness together make up the stability suite. Let’s look at each dimension separately.
Emotional stability (the opposite of neuroticism) is associated with reduced levels of negative emotions, such as fear, sadness, concern, wariness, anxiety, and guilt. Hirsh and colleagues46 found that emotionally stable people tend to report avoiding the following real-world behaviors: taking medication for depression, taking tranquilizing pills, visiting a psychiatrist or psychologist, taking three or more different medications in the same day, sharing a problem with a close friend or relative, misplacing something important, participating in a self-help group, giving money to a panhandler, taking a sleeping pill, and trying to stop using alcohol or other drugs. It’s clear: emotionally stable people are definitely stable!
Emotionally stable people also tend to display fewer occurrences of negative outcomes such as depression, stress, social isolation, and impaired physical health.47 In fact, emotional stability is a very strong positive predictor of a spouse’s martial satisfaction and relationship quality.48 In the sexual domain, Nettle and Clegg49 note, “neurotic individuals undermine their own sexual relationships through relentless worry, suspicion, jealousy, and neediness.” And when it comes to courtship, neurotic individuals may overthink issues so much that they do not act, having too much “approach anxiety” to even get a chance in the mating marketplace. What, then, could be the benefits of low levels of emotional stability for reproductive success?
A person’s level of neuroticism represents his or her threshold for detecting biologically related threats. Anxiety, a major component of neuroticism, increases detection and attention of potentially threatening predators by speeding up reaction to such threats and interpreting ambiguous stimuli as negative.50 Within the mating intelligence domain, neurotic individuals tend to be hypervigilant to potential cues of mating-related threats. In the words of Nettle and Clegg,51 neurotic people have “hair-trigger threat-detectors” that evolved to be safer more than sorry.
The evolutionary logic of the neurotic person is actually quite sound. Take jealousy, something neurotic people are particularly prone to. Although imaginary cases of cheating may cause some relationship difficulties, a few genuine cases may slip through the cracks. Because the costs of cheating are so great for reproductive success, it may well be worth it to worry, at least at a moderate level.
Neuroticism is also related to competiveness and academic success.52 Therefore, the negative effects of neuroticism on reproductive success can also be positive when directed toward the goal of increasing one’s position in the mating domain. For those who can deal with their levels of neuroticism (without it becoming too much of a burden), high neuroticism can be beneficial to reproductive success.
Taken together, in terms of reproductive success, emotional stability can have its benefits and disadvantages. High levels of neuroticism can have disadvantages but can also be adaptive in detecting mating-relevant threats and can be a source of motivation in competition for mates. Let’s look at the next two traits that make up the stability suite.
Scoring high in conscientiousness and agreeableness may seem socially desirable. However, like all the other traits mentioned in this chapter, social desirability is a different animal than the positive effects on fitness (see also Chapter 8).53 Whether we like it or not, natural and sexual selection favors traits that increase reproductive success, including many cases in which this success comes at the expense of others. Fitness can be enhanced, under certain circumstances, by breaking rules and cheating.
It is with these trade-offs in mind that we discuss the highly correlated traits of conscientiousness and agreeableness. Nettle and Clegg54 reported that in a sample of 545 people, men (but not women) with low levels of agreeableness and conscientiousness tended to have a higher number of sexual partners. It has also been found cross-culturally, across 10 world regions, that low levels of agreeableness and conscientiousness are related to higher levels of sexual promiscuity and relationship infidelity,55 so there may be reproductive benefits to those on the low end of these traits (also see Chapter 8). To further explore these correlations, let’s look at conscientiousness and agreeableness separately.
Conscientiousness involves orderliness and self-control in the pursuit of goals.56 Those high in conscientiousness are good at delaying immediate short-term rewards in favor of greater long-term payoffs. Hirsh and colleagues57 found that those scoring higher in conscientiousness tended to report engaging less in variety of behaviors, such as discussing sexual matters with a friend, lounging around the house without any clothes on (if you recall, our favorite!), picking up a hitchhiker, reading a tabloid paper, driving or riding in a car without a seatbelt, swearing around other people, spending an hour at a time daydreaming, shopping at a second-hand thrift store, telling a dirty joke, and listening to music. Bottom line: people high in conscientiousness take better care of themselves and avoid risks. Indeed, conscientiousness is associated with life expectancy.58
People scoring extremely high in conscientiousness tend to have high levels of moral principle, perfectionism, and self-control. This is reflected in the discovery that conscientiousness is found among patients with eating disorders and obsessive-compulsive personality disorder.59 Conscientiousness may be very beneficial to a highly competitive modern world in which high achievers get ahead. Directly in terms of reproduction, those higher in conscientiousness ought to be better parents and more dutiful when it comes to taking care of their children.
According to Robert Sternberg’s triarchic theory of love,60 different components of love can combine to produce different types of love. Intimacy alone is “liking,” passion alone is “infatuation,” and commitment alone is “empty” love. Intimacy and passion combine to form romantic love, intimacy and commitment combine to form compassionate love, passion and commitment combine to form fatuous love, and if you can combine all three components, you get consummate love. Research shows that conscientiousness is positively correlated with both the intimacy and commitment components of Sternberg’s theory of love,61 which would make conscientiousness very well suited to a compassionate form of love. In the words of Engel, Olson, and Patrick,62 “conscientious persons tend to be motivated workers in their love relationships.”
Reasonably high levels of conscientiousness can certainly be conducive to long-term reproductive success. But in some contexts in the modern world, and especially in most of the unpredictable and harsh environments in which our ancestors evolved, high levels of conscientiousness and the extreme self-control associated with it may be harmful to fitness. In unpredictable environments, it may make more sense, evolutionarily speaking (again, we are not prescribing anything here), to be more open to spontaneous opportunities to enhance reproductive success.
Low levels of conscientiousness may therefore be more conducive to short-term mating success. But why? As Nettle and Clegg63 note,
Less conscientious individuals favor immediate opportunities, with little regard for their future consequences. They are impulsive about pleasures and procrastinate about work. In mating, they are more promiscuous, more likely to be unfaithful, and more likely to have impulsive, unsafe sex under the influence of alcohol or drugs.
Maybe those with low conscientiousness are just more impulsive and opportunistic, and that is why they have a higher number of sexual partners. Research shows that highly conscientious people report fewer short-term mating partners as well as avoiding opportunities to take an immediate reward that could be to their short-term advantage.64 Low conscientiousness is related to delinquency, antisocial behavior, impulsiveness, unfaithfulness, and sexual intercourse under the influence of drugs or alcohol.65 There’s no doubt: conscientious people exert greater self-control.
Like all the other traits mentioned in this chapter, there are clearly trade-offs to reproductive success. Clusters of traits that orient the person toward working for long-term payoffs will tend to reduce opportunistic immediate rewards but may also decrease risk for getting a sexually transmitted disease, jealous partners, and a bad sexual reputation.66 Depending on the context, the relative weighing of the costs and benefits for reproductive success will differ.
Whereas conscientiousness has to do more with responsibility and a sense of duty, agreeableness is more tied to empathy and the desire to please others. Indeed, agreeableness, empathy, and theory of mind are intimately connected (see Chapter 7).67 Those who register others’ emotions, can feel others’ pain, and are aware of others’ mental states tend to also be highly agreeable. Hirsh and colleagues68 found that those scoring higher in agreeableness tended to report giving more money to panhandlers, participating in more self-help groups, taking more tranquilizing pills, drinking less in a bar, producing less works of art, riding fewer horses, misplacing things that are important, riding less in taxis, using thermometers more to take temperature, and drinking less beer. In general, women tend to score much higher than men on measures of agreeableness,69 and agreeableness is related to higher-quality friendships, successful parenting, better academic and career performance, health, and life satisfaction.70
We humans (with apologies to the orangutans reading this book) appear to be unique among mammals in how well we cooperate with people not genetically related to us. Because humans are such a social species, we may have been under strong evolutionary selection pressures to pay attention to the mental states of others.71 Agreeableness is associated with all three of Sternberg’s love dimensions—passion, intimacy, and commitment72—which would make agreeableness the Big Five trait most directly associated with a consummate form of love. This is not surprising because agreeableness and its associated mental states and emotions are highly advantageous to facilitating harmonious relationships and avoiding violence, aggression, and hostility.73
Although highly agreeable individuals display less infidelity and show increased loyalty to mates, they also have fewer lifetime sexual partners.74 Agreeableness may even sometimes be detrimental to short-term mating success (see Chapter 8 for more on the allure of the bad boy).75
Therefore, highly agreeable people are very much valued as friends and long-term partners but may also miss out on sexual opportunities and have impaired status competition, both outcomes potentially relating to reproductive outcomes. A study of male business executives found that agreeableness negatively predicted career success, with nice guys finishing last in the competition for status and money.76 Of course, agreeable individuals may just not be as driven to have a high number of sexual partners, which could explain their lower total number of sexual partners (see Chapter 8).
It seems unlikely that always caring for the needs of others is conducive to fitness under every circumstance. Although having empathy is surely helpful for most of social life, it also bears costs in terms of leaving one open to exploitation and inattention to personal fitness gains.77 The balance of advantages and disadvantages between different levels of agreeableness will therefore depend on the context. In small, isolated groups with a limited number of people and where contributions are public,78 high levels of conscientiousness and agreeableness may be more evolutionarily adaptive than in a big city where there are looser social connections or in situations where competition is required (as opposed to cooperation). We take up these issues again in Chapter 8.
Extraversion and openness to experience form the core of plasticity.
Extraversion is intimately tied with exploration, particularly in social situations.79 Extraversion is also associated with positive emotions. As part of the plasticity factor, extraversion is tied to the dopaminergic neurotransmitter system.
Extraversion is associated with short-term reproductive outcomes in men.80 Men who are more extraverted tend to be more popular in a speed-dating context,81 have a higher number of sexual partners,82 and also tend to cheat on their current mate or end their current relationship for another.83 Extraverted women, compared with introverted women, get more sexual invitations from men.84 Extraverted women also tend to show reduced levels of choosiness in a speed-dating context.85
Although extraversion preferences tend to be equally strong in both sexes in student samples,86 when one looks at members of dating agencies, people dating, and newlyweds, one finds a tendency for men (more than women) to prefer introversion in their mates.87 What is clearer is that both men and women prefer extraversion for a short-term encounter relative to a long-term encounter.88
The high energy and positive mood of extraverts may allow them to obtain mates of higher quality than someone who may be more introverted and not as prone to seek out other mating opportunities. Extraversion is also related to sensation seeking, the passion component of Sternberg’s triarchic theory of love, and people high in extraversion are more likely to have more social support and gain reward from social engagement.89
In the study by Hirsh and colleagues,90 those higher in extraversion were more likely to tell a dirty joke, plan a party, entertain six or more people, volunteer for a club or organization, get a tan, attend a city council meeting, color their hair, go to a night club, and drink in a bar. Clearly, extraverts engage more in the social world and exhibit behaviors (e.g., coloring their hair) that have social and mating implications.
The very same advantages of extraversion for a short-term mating strategy, in certain contexts, may be disadvantages. For instance, having too much sexual diversity and social exploration can be risky in terms of health as well as forming and maintaining a long-term relationship. Those who are higher in extraversion tend to be hospitalized because of an accident or illness more frequently than those lower in extraversion.91 Those high in extraversion also tend to be arrested more and become involved in criminal or antisocial behaviors.92 Also, the extraverted tendency to jump from relationship to relationship means that the children of extraverts may have a higher probability of being exposed to stepfathers, a known risk factor for child well-being.93
Clearly there are reproductive trade-offs for extraversion. Reproductive goals and environmental circumstances call for different levels of the extraversion continuum. This constant fluctuation of the “optimal value” during the course of human evolution meant that natural and sexual selection could not settle on an optimal value, allowing individual differences in extraversion to remain.
Of all the Big Five domains, the openness to experience domain of personality (sometimes referred to as openness/intellect) is the most cognitive. Therefore, this particular dimension of personality may undergo the highest mix of selection pressures, including both mutation selection and balancing selection.
Intellect and openness are substantially correlated with each other and reflect an interest in truth and beauty, respectively.94 Consistent with this, Hirsh and colleagues95 found that those scoring higher in the openness/intellect domain tended to report higher levels of the following: producing works of art, reading poetry, painting a picture, writing poetry, buying a book, reading a book, attending an art exhibition, making a gift for someone, attending an opera or orchestra concert, and attending a ballet performance. Considering the mix of intellectual and creative aspects of the larger openness/intellect domain, Gerard Saucier’s96 suggestion that “imagination” is a better label for this domain seems quite reasonable.
Although openness is often combined with intellect, the two constructs can also be separated from one another. In fact, this separation is crucial to mating intelligence. In a recent analysis, researchers conducted a large-scale analysis of 15 scales measuring facets of openness/intellect.97 Even though the two facets were related to each other, they also were at least partially separate in terms of their correlations with more than 2,000 personality items taken from the International Personality Item Pool.98
The kinds of items that related to Intellect reflected engagement in intellectual matters and perceived intelligence (e.g., “Like philosophical discussions,” “Am quick to understand things”). On the other hand, openness was related to personality traits reflecting engagement in sensation and perception (e.g., “Believe in the important of art,” “See beauty in things that others might not notice”).
Recent brain and behavioral research provides further support for the partial separation of intellect from openness. In one sample of 104 healthy adults, intellect, but not openness, was related to the ability to update working memory representations and the brain areas associated with that activity in the left lateral anterior prefrontal cortex and posterior medial frontal cortex.99 Intellect was also associated with IQ scores. The association of intellect with brain activity could not be entirely explained, however, by cognitive ability. This is most likely because intellect reflects both the ability and the desire to engage in the intellectual realm.
If openness, by itself, is not related to conscious, rational, deliberate thinking, what is it related to? From a personality perspective, we already noted that openness is related to extraversion, and both may be tied to the functioning of the neurotransmitter dopamine. However, personality dispositions affect cognition (and vice versa). Dopamine can affect both behavior and thought. Cognitively speaking, openness is associated with apophenia (seeing patterns where they do not exist),100 an enhanced ability to implicitly learn the probabilistic rule structure of the environment,101 and an inability to ignore stimuli that were previously tagged as irrelevant (the technical term for this is latent inhibition.102)
But here’s where things get really interesting. On the one hand, people with high levels of openness tend to be more creative, particularly in the arts.103 Indeed, many creative pursuits require a heightened engagement and sensitivity to the sensory world, and individuals with higher levels of openness, and its associated state of cognitive disinhibition, may be more likely to see connections that others may not notice.104 On the other hand, openness and its associated cognitive states also show linkages to a proneness to psychosis.105 Openness is associated with altered states of consciousness and unusual perceptual experiences such as vivid imagery and magical thinking.106 These traits are sometimes referred to as the positive aspects of schizotypal personality disorder, a milder form of schizophrenia.
What does all of this have to do with mating? Well, schizotypy is also related to short-term mating success. One study on practicing poets, artists, and control subjects found that perceptual-cognitive distortions predicted creative output, which in turn predicted lifetime number of sexual partners.107 Another recent study found that among males, a general tendency to engage in creative activities across the performing arts, science, writing, and visual arts, was related to total number of sexual partners within the past year. Schizotypy was indirectly related to number of sexual partners through its relationship with creative activity.108 Other research has confirmed this link between positive schizotypal traits and a short-term mating strategy, as indicated by reduced levels of long-term investment (see also Chapter 7).109
Therefore, the unusual thinking style characteristic of openness can lead to highly creative and imaginative ideas about the world, or to full-blown psychosis. Although there is still some debate about the precise nature of the relation between openness to experience and schizotypy,110 and this is still very much an open area of exploration, the bulk of the evidence suggests that the effect of openness on mating depends on other traits of the individual.
Individuals high in openness but in poorer condition without protective functions such as intelligence and working memory111 can appear disorganized, incoherent, delusional, low in emotional expression, and impaired in perspective taking and can appear to have a bizarre, unfunny sense of humor. This combination (high openness and low condition) may repel potential mates and represent what Shaner, Miller, and Mintz112 refer to as a “catastrophic failure of mating intelligence.” Indeed, there is evidence that people with schizophrenia do have lower levels of reproductive success.113
On the other hand, those with high levels of openness, who exhibit schizotypal-like traits and who can deal with the influx of emotions and cognitions they experience, can be extraordinarily attractive to potential mates, exhibiting a terrific sense of humor, an accurate theory-of-mind, emotional expressiveness, and the ability to tell engaging stories. Indeed, many creative people of great recognition and accomplishment display the positive symptoms of schizotypy (the milder form of schizophrenia), and these individuals have plenty of mating success, particularly in short-term contexts (also see Chapter 7).114
Because the fitness payoffs to openness to experience seem so highly dependent on environmental conditions and other mental and personality characteristics of the individual, it would make sense for balancing selection to maintain a significant source of variation of openness in the general population.
Understanding the evolutionary origins of variations in personality is highly relevant to understanding human mating intelligence. Traits cluster in evolutionarily predictable ways that served fitness-enhancing functions among our ancestors in a number of different contexts. Each particular trait also can be related to trade-offs in reproductive strategy. Throughout the course of an individual’s life span, different contexts can differentially activate different genes. The dynamic interplay between nature and nurture within an individual’s life span is highly complex and mutually enforcing. How personality affects mating depends both on the context and condition of the individual.
Mate choice often happens fast, with men and women (often unconsciously) deciding whether a person is an appropriate long-term partner within the first few minutes of meeting him or her.115 Although a number of social, economic, ecological, and psychological forces certainly play a role in this initial attraction,116 biological forces are at play as well (see Chapter 4), including bodily and facial symmetry, ovulatory cycle effects, and the scent of those with dissimilar histocompatibility complex (MHC) genes involved in the immune response.117
A particularly understudied biological process is the contribution of biological systems that are likely to underlie universal human personality traits. People are typically (but certainly not always) correct in their initial perceptions of personality, even after meeting someone for only a few seconds (also see Chapter 8).118 Since personality perception happens fast, and plays a role in mate selection, an interesting question is: what kinds of personalities tend to be attracted to one another, and what are the biological systems that make up the relevant personality factors?
To explore this question, Helen Fisher and colleagues119 examined the role of temperament in the initial attraction phase of mate choice. They identified four interrelated yet different neural systems that are associated with a unique suite of biobehavioral traits and developed a self-report measure to tap into individual differences in each of these systems. The four systems are (1) the dopamine and norepinephrine systems, which are related to each other and are linked to the meta-trait plasticity, (2) the serotonin system, which is linked to the meta-trait stability, (3) the testosterone system, which is linked to heightened attention to detail, intensified focus, restricted interests, spatial acuity, aggressiveness, and social dominance, and (4) the estrogen and oxytocin systems, which are associated with each other and are linked to verbal fluency, empathy, nurturance, bonding, social connection, and other prosocial skills.120 Of course, these four hormone systems interact, and it is possible for individuals to score high on more than one dimension. Still, people differ in terms of which hormones are most dominant.
In a sample of 28,128 participants taken from the dating website Chemistry.com,121 the researchers found that men and women who reported higher levels of traits associated with the dopamine/norepinephrine system were more likely to seek out others with similar traits.122 The same pattern was found for those reporting higher levels of traits associated with the serotonin system. On the other hand, those expressing traits associated with the testosterone system were more likely to choose to meet those expressing traits associated with the estrogen/oxytocin system. In sum, they found that like tended to attract like in terms of those expressive of dopamine/norepinephrine and serotonin, but opposites attracted among those expressive of the testosterone and estrogen/oxytocin systems. The researchers concluded that aspects of biology play significant roles in the initial phase of mate choice (of course, environmental and cultural factors play a huge role here as well).
Therefore, it would seem that the predictors of attraction are very specific to the individual, and are not necessarily the same predictors of relationship and life satisfaction. Fisher’s research suggests that those who like to explore the world tend to be attracted to like-minded explorers. Those who are dutiful and emotionally stable tend to be attracted to others who are stable. Those expressive of testosterone may be drawn to those high in estrogen because these partners have the verbal and social skills and the compassion that the higher-testosterone individual needs. At the same time, those predominantly expressive of estrogen may be drawn to those expressive of testosterone because they need the high-testosterone person’s decisiveness, directness, and analytical and spatial skills. We hope that in the future researchers will investigate the impact of hormones on attraction and how initial attraction affects short-term and long-term mating success.
Of course, hormones are constantly changing in every individual and are influenced by contextual factors, such as age, stage of a relationship, and even particular interactions. For instance, research shows that men exhibit a spike in testosterone after trying to impress an attractive woman.123 Hormones also naturally fluctuate through the course of a relationship and as people age.124 These fluctuations can affect the mating domain. For instance, one study reported that as people age, they tend to report lower levels of passion and higher levels of intimacy and commitment,125 a personality profile that is no doubt influenced by hormonal changes. Therefore, it may not be such a surprise that initial attraction is not always be the best predictor of long-term relationship satisfaction and that the person we are initially attracted to does not always make the best long-term mate.
For instance, although extraversion is associated with passion, passion is negatively associated with relationship length.126 Therefore, two people high in extraversion may be attracted to each other, but their relationship can fizzle out once the passion fades. To keep the relationship going may require high levels of other personality traits, such as agreeableness and conscientiousness. Indeed, both agreeableness and conscientiousness are related to the intimacy and commitment components of love, and intimacy and commitment are positively correlated with relationship length. There seem to be only minor differences between males and females in these personality-relationship correlations, so both sexes can benefit in relationships by working on their personality (which can alter their hormones).
We told you mating intelligence was complex! But hopefully we have demonstrated the usefulness of mating intelligence in making sense of the complex role personality plays in human mating, especially in terms of individual differences. In the previous chapter, we took up the role of cognitive abilities in human mating, and in this chapter we took up personality. That concludes the courtship display aspects of mating intelligence. For the remainder of the book, we turn to the many mechanisms humans have in place for selecting a mate and navigating the windy road of mating. Next up, we’ll discuss other traits that can increase attraction, how all of these various cues become integrated in perception, and how this all plays out in the real world.