LAUREN Clarke is an eldest child.
She is conscientious, hardworking and has always been an overachiever.
She has a leadership role in the company where she works and is very career-driven. She said she often felt pressure to achieve but enjoyed the thrill of doing well.
Her younger sister Marissa is bright and bubbly and always socialising. She is pursing a career in acting after taking a few years off to travel the world.
She said she often felt that she would never be as smart as her older sister and instead pursued activities she knew she would be able to excel at in her own right without competition.
Both Lauren and Marissa fit the profiles of a classic eldest and youngest child.
University of Sunshine Coast psychology lecturer Rachael Sharman is not surprised.
She said that while DNA and environmental factors largely contributed to the development of personality, so too did the birth order.
Studies on the effects of birth order and personality have been well-documented, focusing on the fact that whether you are eldest, middle, youngest or an only child, your birth order can reveal a lot about your personality.
Research has focused predominantly on first-borns and their propensity for success.
One Norwegian study of 1.5 million people found first-borns at the highest income and education levels of the order line, regardless of family income levels.
Ms Sharman said this could be because first-borns were the sole recipient of parents' affections before other children came along, so they tended to be more adult-orientated and confident.
First-borns often are more academically minded and higher achievers.
But Ms Sharman said parenting styles and ways parents treated each child affected personalities more than the birth order.
She said first-time parents tended to be stricter and more rule-focused with their first child and when the second or third child came along, parents were more relaxed.
She cited the example of not letting the first child watch an M-rated movie until they turned 15 but the second child would get to watch such a movie at a younger age.
She said youngest children were often more agreeable: "They're born into a family with rhythm and rules and often they get dragged along to things."
She added that last-borns tended to be liberal and less rules-based than their first-born sibling.
She said while "middle-child syndrome" was bandied about, little evidence was available to substantiate claims that middle-children felt neglected and left out.
"Middle children tend to be their own person. Parental expectations aren't as high," she said.
However, evidence suggested that whatever career a middle-child pursued was likely to be a polar opposite to the career choice of the child above them in line.
And contrary to popular belief, Ms Sharman said an only child wasn't always the stereotypical spoilt brat.
"They actually do better in terms of personality, self-esteem, confidence and academics," she said.
She put this down to not having to share parental resources while growing up.
Clinical psychologist Sally Shepherd agreed parenting styles contributed a great deal to personality but while traits were common in all first-borns, middle children or youngest children, they were not the only defining factor in shaping personality.
"You are not a victim of your birth order. It doesn't have to be that way," she said.
"In the last 10 years, there has been a great deal of research in psychology and neuro-science into the plasticity of the brain."
She said personality traits were not absolute: they depended on a number of variables such as life experience, peer dynamics and family relationships.
Interestingly, Ms Sharman and Ms Shepherd are both first-borns.
What birth order can say about you:
Eldest: First-borns are high achievers and hard workers. Everything they did as a child was a big deal to their parents which gives first-borns confidence and belief in themselves. First-borns are born leaders and take pleasure in caring for others. Parents can place high expectations on first-borns which can lead to a need to please later in life.
Middle: Middle children tend to be very social and are able to adapt easily and deal with all manner of people. Having an older and younger sibling leaves middle-borns able to find common ground and they are able to see both sides in an argument. Middle children can feel like they have to compete with the oldest and the youngest child which can lead to feelings of being alone later in life.
Youngest: Being the baby, youngest children are the centre of attention. They are social and outgoing and feel comfortable with older people which leads to a sense of confidence. They are often the life of the party.
Only: An only child can get along with anyone and is often wise beyond their years. They are independent and, having grown up enjoying their own company, can be creative. They stand firmly to beliefs and are affectionate. Only children can be bossy since they have never had to compete for attention among siblings.
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