Have you heard of Type A, Type B and even Type C personality types? Or maybe you've seen them on social media, where they've been pretty popular recently.
Some self-identify as "Type A", others use it to describe a colleague or a friend with a little roll of the eyes.
A type can be a badge of honour to some and an insult to others.
But, do these personality types have any real value when it comes to understanding ourselves and others?
Where does Type A, Type B and Type C come from?
Nick Haslam, a professor of Psychology at Melbourne University in Naarm, says the idea of Type A and Type B personalities has been around since the 1950s.
In their 1959 research, American cardiologists Meyer Friedman and Ray Rosenman attributed Type A behaviour with ambition, competitiveness, being time-conscious, aggressive and an increased risk of coronary heart disease.
Professor Haslam says "Type A was supposed to be something that might put you at risk of developing heart disease", but it didn't hold up as an accurate predictor.
Psychologist Cailin Jordan lives in Perth on Whadjuk Noongar country and says when people use the Type A term today, it is often to describe someone who is "a bit impatient, a bit uptight, very self-driven".
Type B is usually attributed to those with the opposite traits. "Someone that's a bit more chill, a bit more relaxed," Ms Jordan says
The term Type C is less established, but online it tends to be attributed to a blend of the other two. On social media, it can be someone writing a detailed travel itinerary that is not followed.
In academic circles, Type C behaviour or cancer-prone personality is associated with introversion, passiveness and suppressing emotions.
Researchers Steven Greer and Tina Morris are credited with introducing and naming the personality type as a risk factor for cancer in research beginning in the 1970s.
However, Ms Jordan says it also does not stack up today.
Professor of Public Health at The London School of Hygiene & Tropical Medicine, Mark Petticrew says some of the Type C research was funded by the tobacco industry and the idea of cancer-prone personality is a pseudoscience.
In the case of Type A, he says the "tobacco industry funded the most influential researchers working in the field and were a driving force behind it".
"Type A behaviour was the tobacco industry's red herring."
Why we love to classify one another
These personality types are not diagnostic, but Ms Jordan says there is no harm in categorising ourselves and each other.
"It's a shorthand for trying to understand each other, which is a very natural thing to do."
Professor Haslam says, "people love to have ways to classify one another".
He says terms such as Type A and Type B are popular because they capture some of the real differences between people and how they behave, while also being easy to use.
It might be more accurate to think of characteristics on a continuum or spectrum, Professor Haslam says, but human beings prefer to sort each other into categories.
"People say, 'you're an introvert', 'my boyfriend's an extrovert' and these are just simplifications. They're useful simplifications."
People also use diagnostic categories inaccurately to do this too. "People will say, 'I'm a little bit OCD' where they mean I'm kind of rigid and perfectionistic"
Astrological signs are another popular way people choose to understand and connect with each other, according to Professor Haslam and Ms Jordan.
Helpful 'shorthand'
Ms Jordan says that while these personality types are not evidence based, they can be helpful as "personality shorthand" or "social shorthand".
Professor Haslam says people should "use whatever concepts they find helpful".
However, if people are interested, he says the big five personality traits are "better estimates of what the main dimensions of personality are".
These traits are openness, conscientiousness, extraversion, agreeableness and neuroticism.
'Personality is not fixed'
Professor Haslam says people are a bit more nuanced than these categories — and personality type models in general — allow for.
They also fail to acknowledge how we change, he says.
"If you think of yourself as belonging to a type or even if you think someone else can be captured by a type, you tend to imagine that they'll always be like that ... that sort of limits how we see others, and it probably limits how we see ourselves."
Professor Haslam says people's personalities continue to evolve through adulthood.
"Most of us aren't finished products."
