Imagine you have a friend called Megan who is always full of energy, loves to be around people, and is really enthusiastic. Your other friend Zoë is nothing like Megan; she is shy, quiet, and enjoys being on her own. What is it about these two girls that makes them so different? The answer is their personalities. You probably know lots of people in your family or at school, and they may seem different from each other in all sorts of ways, not just in how sociable or shy they are. This is because they all have different personalities, and this means that no two people are exactly the same.

What Is Personality?

You can think of personality as an individual’s thoughts, feelings, and behaviors that remain the same over time and across situations; we refer to these stable characteristics as personality traits. Scientists have several ideas about the best way to categorize the various traits that make up our personalities (and even about how many categories there are!), but the most popular and widely used framework is known as the Big Five [1]. The Big Five has—you have guessed it—five categories (Figure 1). These are openness, conscientiousness, extraversion, agreeableness, and neuroticism. It can be hard to remember all these categories, but it helps that you can put the first letter of each category together to spell out “ocean.”

For each of the categories, you can imagine placing yourself somewhere along a ruler from low to high. Your friend Megan would probably be high on extraversion (so an extravert), while Zoë would probably be low (an introvert). However, most people are around the middle of the ruler. Scoring higher on extraversion, for example, means that Megan will be more sociable than Zoë in lots of different situations. We all fall somewhere along all five categories, and so our personalities are best understood by combining all five.

Traits do a good job of trying to explain who we are, but it is important to remember that there are other parts of personality that are not captured by traits, like our plans, goals, motives, and a more general sense of ourselves.

How Do We Measure Someone’s Personality?

There are two main ways that scientists can measure someone’s personality. Since personality captures how a person behaves, the first way is to watch what the person does in various situations. If we watch Megan in social situations, we could probably see that she should get a high extraversion score because she is excited, eager to talk to her friends, and happy to play games with them. This might be the best way to measure her personality because her scores would reflect how she actually behaves in the world. However, even if we can see how she behaves, we are unable to see her thoughts and feelings (which are also important), and it is possible that she is only pretending to enjoy playing with her friends. This is the problem scientists face when they only watch how people act.

The other way to measure personality is simply to ask people! After all, people know themselves well. Scientists often use questionnaires that ask people how they usually behave or feel, and the answers are used to compute scores for each trait. For example, you might be asked to say how well the phrase “gets chores done right away” describes you. If you think that this is a very accurate description of you, then you would probably get a high score for conscientiousness. You might wonder whether people will tell the truth when they answer, and this is important to consider, but scientists have lots of evidence that people’s answers show predictive validity. This means that the personality scores people get based on their answers can predict other things. For instance, college students’ conscientiousness scores can predict their grades. If people were not telling the truth, then their answers would not predict their behaviors.

Where Does Your Personality Come From?

You might be wondering where someone’s personality comes from. As with most things in science, there is no simple answer. Your personality is the result of two main influences (Figure 2). One of these is your genes, which were passed to you from your parents. This means that you inherit some of your personality from your parents [2]. Genes explain why biological siblings may be similar to each other personality-wise, even if they grow up in different places. The other main influence on personality is the environment. Because of the experiences you share with the people around you, the personalities that you all have may be similar. For example, if you, your parents, and your siblings all live in a stressful environment, that environment may have a similar effect on all of you. Just as your height is influenced by both your genes (tall parents tend to have tall children) and your environment (people living in places with plentiful food tend to be taller than those where food is scarce), so is your personality.

Does Your Personality Change Over Time?

Scientists have found that personalities change and develop across a person’s lifespan, but this happens rather slowly. For example, as we grow up, most people become more agreeable and conscientious. We also know that life and work experiences can lead to changes in personality. If you have a successful career, this may increase your conscientiousness score and lower your neuroticism score, for instance [3]. Finally, there is some evidence that people can choose to change their personalities by altering their behaviors to try and reach their personality goals [4]! This is great news if you have always wished you were a bit more talkative, or less anxious, than you currently are. It turns out that you might be able to do something about it!

Why Is Personality Important to Understand?

Learning about ourselves and other people is always useful. If Megan is extraverted, then I know she might like it if I ask her to come to a party with me and my family. Understanding how she feels in various situations will help Megan become better at choosing activities, hobbies, and eventually jobs she might enjoy. Scientists have found that measuring someone’s personality can provide information about all kinds of important things. For instance, we know that extraverted and conscientious people tend to live longer, stay married longer, and do better in their careers [5]. Of course, there are plenty of people who are not extraverted or conscientious who also have long lives and marriages and are successful in their jobs. It is important to remember that there are many other things that affect what happens in our lives, like how much education we have or how intelligent we are.

Do Animals Have Personalities Too?

Scientists used to avoid using the word “personality” to describe living things other than people, because they felt that people were “special” and different from other animals. Now it is more common to hear scientists talk about animal personalities. After all, individual animals also show tendencies to behave in certain ways—anyone who has pets will already know this! Animals cannot answer questionnaires about themselves, but their personalities can still be measured by watching them and recording how they behave, or by asking people like zookeepers to fill in questionnaires about the animals. Using these methods, we now know that animals have personality traits. Species that are closely related to us, such as chimpanzees (Figure 3), have something like the human Big Five categories, whereas more distantly related species, such as parrots and octopuses, have different, and perhaps more basic, categories. But there are still surprising similarities across a wide range of species because all animals have evolved from a common ancestor. This is why an extraverted parrot (bold, active) is a bit like an extraverted person. And parrots are often talkative too!

Conclusion

We are all different in terms of our thoughts, feelings, and behaviors. These diverse characteristics make up our personality. Our parents’ genes, combined with our environment, both contributed to the particular personality we now have. Our personality mostly stays the same over time, but there are also some slow changes that happen as we get older, as well as other changes caused by major life experiences. Understanding your personality may help you to figure out what you enjoy the most. Finally, remember that not just people have personalities—your dog and cat do, too! If you have a pet, maybe go and find it now, to see if you can work out which traits your favorite animal might be high or low on!

Glossary

Personality Traits: ↑ Tendencies to act, think, and feel in certain ways that remain the same over time and across different situations.

Openness: ↑ Describes those who are creative and curious, which can help with problem solving. Low scorers tend to be more down-to-earth and practical.

Conscientiousness: ↑ Describes those who are hardworking and organized, which can help with completing tasks. Low scorers are more impulsive and disorganized but may be more flexible and spontaneous.

Extraversion: ↑ Describes those who are talkative, cheerful, and assertive, which can help with leadership. Low scorers are quieter, more reserved, and less assertive, and often enjoy spending time alone.

Agreeableness: ↑ Describes those who are helpful and trusting, which can help with teamwork. Low scorers are more suspicious and critical, but less likely to be exploited as a result.

Neuroticism: ↑ Describes those who are anxious and stressed, but also sensitive to dangers. Low scorers are more calm and secure, tending to have good mental health as a result.

Predictive Validity: ↑ When a score on a scale or measure predicts something else, like a behavior in the real world (for instance, how well you do at work or in school).

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.