Personality: what is it and why it's important!

Hey team,

Today, I’d like to discuss personality, specifically the aspects we can measure. While personality is complex, we have identified domains that provide meaningful insights into how people think, feel, and behave. Back in January I read Daniel Nettle’s “Personality, What Makes You The Way You Are”  and it did a great job of outlining our current understanding of personality with lots of poignant examples. Nettle explains that personality traits are not absolute descriptors of behavior but rather tendencies that manifest across many circumstances, though not necessarily every single one. Obviously, we can’t predict behavior 100% of the time, but these tendencies offer a useful framework for understanding individual differences. 

Despite this variability, personality traits demonstrate a high degree of reliability over time, meaning that individuals tend to maintain their relative standing on these traits across years or even decades. For example, across 12 years personality has a reliability coefficient between 0.65 and 0.85 which is very strong. Let's remember that this value can range from -1 to +1 with 0 representing no correlation.  In contrast, intelligence measures such as IQ have even higher reliability (often above 0.9), making them one of the most stable psychological constructs. 

Understanding these traits reinforces that personality is real, people differ, and some traits are more advantageous in certain contexts. While environment plays a role, personality is largely heritable. By acknowledging these differences, we can have more honest discussions about inequality and design better systems that target key traits like conscientiousness and neuroticism, ultimately helping individuals achieve sustained improvements in life. 

The Five Domains of Personality

Personality is the relatively stable and enduring pattern of thoughts, emotions, behaviors, and motivations that characterize an individual and influence their interactions with the environment. We measure personality through five domains, remembered by the acronym OCEAN: Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism. Each trait exists on a spectrum, with most people clustering near the middle, some slightly below or above, but some falling at the extremes. Let’s break down these domains: 

Openness: Characterized by receptivity to new experiences, abstract thinking, and intellectual curiosity. High openness fosters adaptability and innovation but, at extremes, may lead to impracticality. Low openness leans toward tradition and concrete thinking, promoting stability but potentially resisting beneficial change.

Conscientiousness: Defined by self-discipline, reliability, and goal-directed behavior. High conscientiousness predicts long-term success, as it drives individuals to delay gratification and plan for the future. Low conscientiousness is associated with impulsivity and poor long-term decision-making, which can lead to instability and poor life success.

Extraversion: Relates to social engagement and responsiveness to external stimulation. High extraversion is linked to interest in engaging in high-energy environments and sociability, while low extraversion (introversion) fosters independence and indifference toward “going out” but may result in social withdrawal.

Agreeableness: Represents a tendency toward social harmony and cooperation. High agreeableness promotes trust, warmth, empathy, and a willingness to help others, sometimes at the cost of personal boundaries. Low agreeableness, on the other hand, is characterized by a more assertive, skeptical, or competitive approach to social interactions. Individuals low in agreeableness may be less concerned with maintaining harmony, more comfortable with confrontation, and more willing to prioritize their own interests over group cohesion.

Neuroticism: Reflects an individual’s sensitivity to potential threats and their tendency to experience negative emotions in response to stress. It functions like a hyperactive self-preservation alarm, going off even in response to minor or ambiguous stimuli. Those high in neuroticism are more likely to detect false alarms—reacting to situations as if they are dangerous when they may not be—while rarely missing actual threats. This heightened vigilance can be advantageous in genuinely hazardous environments but often comes at the cost of chronic worry, emotional instability, and increased stress reactivity. In contrast, individuals low in neuroticism have a more muted alarm system, allowing them to remain calm and unshaken even in the face of adversity, though at the risk of sometimes underestimating potential dangers.

A Quick Note on Heritability

Heritability refers to the proportion of variation in a trait that can be attributed to genetic differences within a given population. Twin studies have consistently shown that personality traits have a significant genetic component. For instance, Nettle (2007) cites research showing that openness to experience has a heritability estimate of 57%, extraversion 54%, conscientiousness 49%, neuroticism 48%, and agreeableness 42%. This suggests that while environmental factors do influence personality, genetic factors play a substantial role. 

While genetics play a major role in shaping personality, environmental influences still contribute, albeit to a lesser extent. Adoption studies, particularly those examining unrelated siblings raised in the same household, provide valuable insights into the impact of shared environment. While adopted siblings often share similar home environments, their personalities tend to be no more alike than those of two randomly selected individuals. This suggests that shared environment, such as parental upbringing, socioeconomic status, and household rules, has a relatively weak effect on personality compared to genetic factors. When we say we get something from our parents, as in our work ethic (akin to conscientiousness), we often attribute that to what we saw modeled for us. However, in reality, it is far more likely that whatever genes your parents had that resulted in their work ethic were also passed down to you. Environmental influence instead is likely shaped by non-home aspects, such as peer groups, individual life experiences, and unique personal challenges. 


Why Personality Matters

Personality traits influence nearly every aspect of life, from relationships to career success. Some traits are objectively more advantageous in modern society, particularly conscientiousness, which is a strong predictor of health, wealth, and overall well-being. While each trait has its trade-offs, the reality is that we do not all have the same predispositions, and recognizing these differences allows us to create better-targeted interventions.


Advantages and Disadvantages of Personality Traits

Neuroticism: High neuroticism is associated with emotional instability, heightened stress responses, and increased risk for anxiety and depressive disorders. Individuals high in neuroticism tend to ruminate, overanalyze social interactions, and anticipate negative outcomes, making them more susceptible to mental health struggles. When combined with low conscientiousness, high neuroticism can be a significant predictor of divorce, poor job performance, and difficulty maintaining social relationships. However, neuroticism historically served an evolutionary purpose—those who were more vigilant to threats had a survival advantage. In today’s world, however, low neuroticism tends to be more beneficial, as it allows individuals to navigate life with greater ease, resilience, and optimism.

Conscientiousness:  High conscientiousness is one of the strongest predictors of long-term success. Those high in this trait are disciplined, reliable, and adept at delaying gratification in pursuit of greater future rewards. They are more likely to follow medical advice, manage their finances responsibly, and avoid risky behaviors, as they naturally prioritize future stability over short-term indulgence. However, excessively high conscientiousness can lead to rigidity, perfectionism, and an aversion to spontaneity, making it difficult to adapt when circumstances require flexibility. 
Low conscientiousness, by contrast, is characterized by a tendency to prioritize immediate desires over future well-being. Individuals with low conscientiousness often struggle with self-regulation, making it harder for them to commit to long-term goals like saving money, maintaining a healthy lifestyle, or adhering to structured routines. This isn't necessarily due to a lack of awareness but rather an indifference toward doing what is objectively "right" for their future selves when a more gratifying option is available in the present. As a result, low conscientiousness is associated with impulsivity, poor health habits, financial instability, and a higher likelihood of engaging in substance use or other short-term pleasure-seeking behaviors at the expense of long-term stability.

Agreeableness: Agreeableness reflects a person’s tendency to prioritize social harmony, cooperation, and the feelings of others. High agreeableness fosters warmth, empathy, and a willingness to help, making individuals well-liked and effective in group settings. However, extreme agreeableness can lead to an excessive desire to avoid conflict, making it difficult to set boundaries or stand up for oneself. This can result in people going along with the group even when they shouldn’t, whether it’s participating in reckless behavior, tolerating mistreatment, or failing to challenge bad ideas simply to preserve social cohesion. Low agreeableness, on the other hand, promotes assertiveness, skepticism, and a willingness to push against the grain. While this can sometimes lead to interpersonal conflict or strained relationships, it also provides the freedom to pursue what one genuinely believes to be right, regardless of how it may be received.

Openness to Experience: High openness is marked by intellectual curiosity, creativity, and a willingness to explore new ideas and perspectives. Those high in this trait thrive in dynamic environments, readily embracing novelty and abstract thinking. Their ability to make unique connections between seemingly unrelated concepts fuels innovation and artistic expression. However, at its extreme, openness can lead to excessive abstraction and unconventional thinking, sometimes bordering on disorganized cognition. Low openness, by contrast, fosters practicality, stability, and a preference for familiar, tried-and-true methods. These individuals excel in structured environments that rely on clear, established frameworks. However, their difficulty with novel perspectives can make them less adaptable to change.


References

Nettle, D. (2007). “Personality: What makes you the way you are”. Oxford University Press.