10 Fascinating Psychology Facts About Personality

Birth Order Can Influence Personality—But We’re Not Sure How Much

The idea that the order in which siblings are born affects their personality is not new. Maybe you’ve heard that firstborns are "bossy" or "responsible," while last-born children are "irresponsible" and "impulsive." But is there any science to back up these stereotypes? For decades, pop psychology books have touted the effects of birth order on personality, but we really didn’t have any hard evidence to support the theory.

The idea goes back to an Austrian psychologist named Alfred Adler who came up with the concept of birth order in the 1960s—however, he didn’t actually do any studies on it. Adler actually felt like your psychological birth order—that is, how you perceived yourself to be positioned within your family—probably had a bigger effect on you than the literal order in which you became part of your family.

Since Adler floated his idea, there have been some scientific studies that have found factors like birth order and family size may have some effects on our personalities. 

For example, one study found that birth order may influence your choices of friends and romantic partners—so, first-borns tend to pair up with other first-borns, middle-borns with other middle-borns, and last-borns with last-borns.

One study found that firstborns tended to be leaders and demonstrate traits like emotional stability, but there didn’t seem to be meaningful links for any of the other birth order positions.

Research also suggests that many of the stereotypes commonly associated with birth order—such as firstborns being bossy—don’t hold up.

One study looked at more than 5,000 people from America, almost 4,500 people from the UK, and more than 10,000 people from Germany, to see if the order in which the participants were born had any real bearing on their personalities. 

The participants gave researchers some self-reported information about the five broad dimensions of personality: extraversion, neuroticism, agreeableness, conscientiousness, and openness.

The researchers found that while first-born children did tend to score better on intelligence tests, there was little evidence to support any real connection between birth order and a person’s character.

Another study that looked at high schoolers didn’t come up with any real link between birth order and personality traits or intelligence.

While the research does not mean that birth order has no influence on personality, it does suggest that there’s still a lot we don’t know about how they might be linked.

Your Personality Is Relatively Stable Throughout Your Life

Do you think that your personality can change over time or is your basic temperament set in stone? Long-term studies of personality suggest that the core parts of our personality remain stable throughout our lives.

According to researcher Paul T. Costa Jr., our personality stays relatively stable as we grow older. In a New York Times article, Costa said "what changes as you go through life are your roles and the issues that matter most to you. People may think their personality has changed as they age, but it is their habits that change, their vigor and health, their responsibilities and circumstances—not their basic personality."

Studies have suggested that many of the personality traits we develop as kids will still be there when we’re adults.

The three aspects of our personalities that do tend to change as we get older are anxiety, friendliness, and eagerness for new experiences. 

Researchers have noted that extraversion and neuroticism tend to decline as we age, while conscientiousness and agreeableness tend to increase. Openness tends to peak when we’re teens and young adults and declines later in adulthood.

That said, studies have also suggested that there doesn’t seem to be a cut-off age at which you can no longer go through personality changes—even into your 70s and beyond.

Change is not necessarily a bad thing, either. Studies have shown that the personality changes that happen later in life can often be positive. 

For example, one study suggested that one of the core traits that tend to get better with age is agreeableness—so no, you’re not necessarily going to get grumpier as you get older.

Older folks may also feel like they’re better able to “take life as it comes” and appreciate the little things without stressing out about stuff that worked them up when they were younger.

For example, extraversion and neuroticism tend to decline while conscientiousness and agreeableness tend to increase. Openness tends to peak during adolescence and young adulthood and declines during later adulthood.

Your Personality Might Be Linked to Certain Illnesses

In the past, there were a ton of theories that specific mental traits were linked to physical ailments—for example, hostility and aggression were often linked to heart disease. 

When put to the test, some studies did show a possible link but others came up with no evidence to support the idea that your personality could influence your physical health. 

Researchers have used a statistical technique called meta-analysis to look at studies on the connection between personality and disease. Through reviews, they’ve uncovered some previously unnoticed connections between neurotic personality traits and a few specific illnesses: headaches, asthma, arthritis, peptic ulcers, and heart disease.

We know stress can wreak havoc on your mind and the rest of your body. So, if you’re a person who is not able to handle stress well, it makes sense that it could take a toll on your physical and mental well-being over time. 

Some studies have suggested that your personality traits can even predict your long-term health outcomes—for example, how likely you are to develop chronic medical conditions or have functional mobility limitations.

One example is “type A” personalities—people who are fastidious, competitive, impatient, and even aggressive a times. One study found that people who reported more “type A” traits were more at risk for high blood pressure—a health condition that can be affected by stress levels. 

Your personality could even influence how long you live: One study suggested that shyness could be linked to a shorter lifespan. Another study on more than 26,000 participants found that people who scored high in traits like calmness, empathy, tidiness, curiosity, and maturity, and scored low on impulsivity, had a lower risk of dying from any cause during an almost 50-year follow-up.

Your Pets Have Personalities...

Many pet owners feel like their pets have personalities that make them totally unique from any other member of their breed. If that sounds like you, there might be some research to back up your perception of your loyal companion. 

Animals from nearly every species—cats and dogs to spiders, birds, and elephants—have been found to have their own personalities. They have their own preferences, behaviors, and quirks that are, not unlike ours, often the same throughout their lives.

While some critics argue that this is us giving human traits to animals (what’s called anthropomorphism), animal personality researchers have seen consistent behavioral patterns that can be scientifically measured and tested, which gives some credibility to the claims. 

For example, psychologist Sam Gosling at the University of Texas-Austin has extensively studied animal behavior. One of the more unusual discoveries he’s made is that male hyenas tend to be more neurotic “scardy-cats,” and females are more dominant. That observation actually makes sense, because female hyenas are physically larger than males. 

Gosling’s also thought a lot about how different animal behavior might seem quite familiar to humans.

"Whereas an introverted human will stay at home on a Saturday night or stand alone at a party, an octopus will stay in its den during feeding and attempt to hide itself by changing color," says Gosling. 

Of course, most of us don’t have hyenas as pets, but researching a wide range of animals will help us understand how personality might shine through in different species. 

Studies on animals you’re more likely to call your own, especially dogs, have suggested that certain breeds really are more likely to have particular traits—and it’s in their genes. 

For example, one study looked at more than 14,000 dogs (101 different breeds) who had been scored with a “pet personality quiz” (basically, a metric that the researchers came up with to help quantify the pups’ traits). Then, they tried to match up the personality traits with data collected from doggie DNA.

When the researchers looked at traits and genetics by breed, they noted that certain traits seemed to link up with certain genes. So, it wasn’t surprising that traits like trainability seemed to be highly heritable. 

What was kind of surprising was that the genes linked to traits like trainability in dogs were found in similar spots in the DNA that you would find traits like intelligence if you were looking at human DNA.

The researchers pointed out that the study was limited and not meant to say that certain traits can be definitely linked to certain breeds. Instead, it just shows that there’s still a lot to learn about how personality in animals could take shape, and that it might be more familiar to us than we realize. 

…And Your Pet Choice Might Match Your Personality

Would you consider yourself more of a "dog person" or a "cat person"? According to one study, your answer may reveal your personality. 

Gosling, the researcher from UT Austin, has also studied pets and human personality.

In a study of 4,500 people, the researchers asked the participants whether they were “dog people” or “cat people. The participants also filled out a survey that measured broad personality traits like conscientiousness, openness, neuroticism, and agreeableness.

The researchers found that the people who identified as “dog people" tended to be more extroverted and eager to please others, while those who described themselves as “cat people” tended to be more introverted and curious.

Gosling says the results could have real-world value—for example, in pet therapy. By using personality screenings, therapists might be able to match people in need with animals that are best suited to their personalities.

Research has also suggested that when your personality matches your pet’s, it might make your bond with them stronger. For example, people who felt like they shared personality traits with their pets reported feeling more attached to them. 

There Are (Probably) Five Core Personality Traits

Researchers have long debated how many personality traits there actually are.Gordon Allport suggested that there were as many as 4,000 distinct personality traits, while Raymond Cattell proposed that there were only 16.

If you’ve ever taken an online personality test, chances are you’ve come across the “Big Five.” Many personality researchers have gotten behind the five-factor theory of personality. This theory includes five broad personality dimensions that make up human personality:

Today, many personality researchers support the five-factor theory of personality, which describes five broad personality dimensions that compose human personality:

1. Extraversion
2. Agreeableness
3. Conscientiousness
4. Neuroticism
5. Openness

Here are some other words that fall into these personality trait categories: 

• Extraversion: Sociable, outgoing 
• Agreeableness: Kind, empathetic 
• Openness: Creative, curious 
• Conscientiousness: Thoughtful, helpful 
• Neuroticism: Sad, anxious 
  

All of these traits exist on a spectrum, and we all fall somewhere along the range in terms of how much we are or are not like each trait. 

For example, some of us are closer to the “extraverted” side of the scale and we like being around other people a lot. Some of us are on the opposite end and are more introverted, where we need to be alone and have time for ourselves to recharge. 

It’s the places where we lean more toward one end of the spectrum than the other that we can see what our strongest traits are. That said, some researchers have pointed out that while the Big Five might give you an idea of your personality, there’s a lot that goes into determining what traits you have. 

For example, your life experiences, genes, the culture you grew up in and live in, and your overall physical and mental health affect what personality traits you do (or don’t) have at various times in your life.  

If you took the Big Five test when you were a teen and retook it when you hit middle age, you might be surprised that some aspects of your personality have changed while others have stayed pretty much the same.

Why You Like What You Like and Don’t Like What You Dislike

It might seem obvious that your personality affects your personal preferences, but you may not really just how much influence your personality can have on what you like and don’t like. From your choice of friends to your taste in music, your unique personality can affect nearly every choice that you make in your daily life.

For example, research suggests that your personality might play a role in your political preferences. One study done by researchers at the University of Toronto found that people who identified as conservative scored higher in personality traits like orderliness, and people who self-identified as liberal were higher in empathy.

Looking at the results, the researchers suggested that since our personalities may drive us to preserve order or express empathy, they could influence our decision to vote for one candidate over another. 

That said, personality and preference aren’t the be-it-end-all. We still have the power to make choices.

For example, even if you tend to prefer that things stay the same, you might vote for a candidate who is proposing a change that would bring order to your community—for example, putting a stoplight in a chaotic, confusing intersection. 

On the other hand, even if you’re generally excited about new experiences, you might not support a candidate who wants to do something in your community that would feel restrictive—for example, implementing an 8 PM town curfew. 

And while we may know our preferences for the kind of work we’d like to do, it doesn’t always mean that’s how it’s going to play out for us in life. You’ve probably had at least one job that you disliked, or that you felt like you had to hide your true self at.

In reality, we don’t always have the luxury of choosing a job that fits our personality well. And even if we do, there’s no such thing as a “perfect job.”

But if you do have the opportunity to think about changing careers, looking at your personality and preferences could help you find a better fit. 

In fact, the Myers Briggs Type Indicator (MBTI)—one of the most popular personality tests—was actually designed to help women who were getting jobs for the first time in their lives while their husbands, fathers, and brothers were away fighting during WWI figure out what kind of work they’d be good at and like doing.

Social Media Doesn’t Necessarily Hide Your Real Personality

When we think about social media, we often assume that most people are presenting an idealized version of their lives. It’s easy enough to do since we can choose what we want to share (or not). 

Whether it’s filtering a selfie before we post or begging a friend to untag us in a photo that’s not very flattering, we do have the ability to curate the image that’s associated with us online. We also get to more tightly control what we say—for example, crafting a comment until it hits just the right note. 

Even if we think we’re taking steps to hide our “true” selves online, our social media profiles might actually tell people a lot more about who we really are than we realize. 

Surprisingly, one study found that your Facebook profile is actually pretty good at conveying your real personality. 

Gosling—the researcher who studied animal personalities—has also done quite a bit of research on human personality. 

In one study, the researchers looked at the online profiles of 236 U.S. college-aged people. The participants filled out questionnaires that were designed to measure personality traits including the Big Five (extraversion, agreeableness, conscientiousness, neuroticism, and openness.

Observers in the study then rated the personalities of the participants based on the online profiles. The observations were then compared to the results of the personality questionnaires that the participants took. The researchers found that the observers were able to get an accurate “read” on a person's true personality just by looking at their Facebook profile.

Gosling said that one reason social media platforms like Facebook, Instagram, and others have become such a huge part of our lives is probably because they do let us share who we are. 

“First, it allows profile owners to let others know who they are and, in doing so, satisfies a basic need to be known by others,” says Gosling. “Second, it means that profile viewers feel they can trust the information they glean from online social network profiles, building their confidence in the system as a whole."

When other researchers have looked at links between how we use social media and our personalities, they also found that certain activities seem to be linked with certain traits.

One analysis of studies found that extroverts tended to spend more time interacting with others on social media, while people who scored highly in conscientiousness tended to spend a lot of time on social trying to learn about others.

Studies have also shown that the words we use to communicate on social media might be influenced by our personalities, too. For example, in one study, words like “love” and “party,” predicted posts by people with more extraversion, while words like “family,” and “week” predicted posts from people with more conscientiousness traits.

One personality that may not be as accurately represented on social media? Neuroticism. Studies have suggested that people who score high in neurotic traits tend to present less authentic versions of themselves online.

Some studies have actually linked neurotic personality traits to a reliance on social media that is even unhealthy, and marked by intense feelings of “FOMO” and unrealistic expectations or comparisons.

There Are Mental Health Conditions That Affect Personality

An estimated that 9.1% of adults in the United States have symptoms of at least one personality disorder. Two of the most common personality disorders are obsessive-compulsive disorder and borderline personality disorder.

Personality disorders are grouped into clusters: A, B, and C.

Cluster A personality disorders are those that come with unusual thoughts and behaviors. Examples of cluster A personality disorders are:

• Paranoid personality disorder
• Schizoid personality disorder
• Schizotypal personality disorder
  

Cluster B personality disorders are those that involve intense emotions, thoughts, and behaviors that tend to change—often quickly. Examples of cluster B personality disorders include: 

• Antisocial personality disorder
• Borderline personality disorder
• Histrionic personality disorder
• Narcissistic personality disorder
  

Cluster C personality disorders are characterized by anxiety and fear-driven behavior. Examples of cluster C personality disorders include:

• Avoidant personality disorder
• Dependent personality disorder
• Obsessive-compulsive disorder 

Your personality does not determine whether you’ll develop a personality disorder, though. Researchers know there are several factors contribute to personality disorders, including: 

• Genetics
• Relationships with peers
• High sensitivity
• Verbal abuse
• Childhood trauma

Psychological researchers are learning more and more about personality disorders with the goal of making sure that people can get diagnosed and treated. Research progress is helping us combat mental health stigma and has even upended some old beliefs and diagnoses that we know don’t capture the full picture of personality disorders, which are complex. 

For example, in the most recent update to the manual that providers use to diagnose mental health conditions (DSM-5), what used to be called “personality disorder not otherwise specified” was replaced with “personality disorder-trait specified (PD-TS)” to account for people who have symptoms of a personality disorder (or even more than one) but don’t meet all the criteria for a specific diagnosis.

Being Totally Defined by a Single Personality Trait Is Pretty Rare

Psychologist Gordon Allport came up with the idea of cardinal traits, which are those that dominate your life to the point where it’s what you are known for and even identified by. 

It was an interesting idea, but it’s considered pretty rare for these traits to wholly define a person. For most people, personality is a mix of traits. There are those that make up the core foundation of their personality (central traits) and traits related to preferences, attitudes, and situational behaviors (secondary traits).

There are some examples of cardinal traits being linked to people in history—so much so that their names have become another term for a type of personality.

Here are some examples you’ve probably heard of from real life, myth, and fiction: 

• Freudian
• Machiavellian
• Narcissistic
• Don Juan
• Einstein 
• Mother Teresa 
• Scrooge