Are middle children better diplomats? The eldest most successful? Where you land in your sibling line-up has long been thought to influence your personality, success and overall identity.

But is any of it backed by sound science?

Research into the significance of birth order was first championed by Austrian physician Alfred Adler in the 1920s, but despite his wealth of work, many of his findings have since been dismissed due to a lack of scientific reasoning.

According to Adler, first-borns were likely to enjoy higher achievements, middle children a higher level of sociability, the youngest likely to be the most rebellious and only children he believed to be successful yet selfish.

Over the years studies have both agreed and disagreed with Adler's various findings. So from eldest to youngest, we’ve dug up all the best research on how the pecking order can affect who you are.

Though a recent study which found that eldest children are likely to be ‘more extroverted, agreeable and conscientious’ than their siblings has been denounced as largely meaningless by its own project leader, other research backs the same conclusions.

One notable study conducted by Feifei Bu at the Institute for Social and Economic Research, University of Essex, found that the eldest child, especially if female, is statistically more likely to be the most ambitious and well-qualified of their family.

The 2014 study concluded that firstborn children tend to carry higher aspirations, which play a significant role in determining their higher levels of attainment.

Famous first borns include J.K Rowling, Sheryl Sandberg, Hillary Clinton and Beyonce.

Key characteristics:

• Confident
• Hard working
• Ambitious
• Competitive

We’ve all heard about how middle child syndrome can brew up feelings of neglect and isolation that children many carry into adulthood. But is it actually true?

Research, which ironically is thinner on the ground for middle children compared with the eldest and youngest, is divided. One study from Stanford University claims that as a result of being neither the celebrated first-born nor the forever babied youngest, the middle child becomes the most envious, least bold and less talkative sibling.

Others however, have found middle children to be the most sociable, the most flexible and the most co-operative of their siblings. Katrin Schumann, an educational consultant and co-author of book The Secret Power Of Middle Children, told MailOnline:

“We discovered during our research, the stereotype does not correspond to reality. Far from being doomed to failure and loneliness, middle children are more likely than their siblings to be successful and enjoy strong social lives and flourishing careers.”

Famous middle children include Stella McCartney, Madonna, Julia Roberts, Martin Luther King and Bill Gates.

Key characteristics:

• Adaptable
• Sociable
• Diplomatic
• Quiet

An outgoing attention seeker or fun-loving and confident? According to research, whichever way you spin it, personality differences are normally most apparent between the eldest and youngest child.

"Firstborns are held to a higher standard. As kids come into the birth order, parents loosen up,” explains Dr. Kevin Leman, a psychologist and the author of The Birth Order Book and The First-Born Advantage.

During his research, Leman found youngest children tend be social and outgoing, but can also be manipulative. “They got away with murder as kids and know how to get around people,” he notes.

A YouGov poll recently revealed that as the youngest child you’re also likely to be funnier than your older siblings, easy going in comparison and more relaxed.

Famous youngest children include Angelina Jolie, Jennifer Lawrence, Cameron Diaz, Steve Martin and Eddie Murphy.

Key characteristics:

• Outgoing
• Relaxed
• Funny
• Manipulative

Only children tend have many of the same personality traits as first borns – confidence, an outgoing yet responsible nature and good organisation skills. However, studies also warn that since they don’t need to share toys or attention with siblings, only children can run the risk of becoming selfish.

The 'little emperor' rule isn’t a hard and fast one however, as one research paper notes:

“The only child is automatically stigmatised. When asked to describe personality characteristics of an only child, many people will respond negatively, indicating the presupposition that only children are spoiled brats.However, research conducted by Falbo, a psychologist known for work in the area of birth order, indicates otherwise.”

“Falbo found that Chinese only children fared no worse in personality or achievement than their counterparts with siblings. However, only children are also often seen as high-achieving, motivated, and successful.”

Famous only children include Natalie Portman, Drew Barrymore, Maria Sharapova and Charlize Theron.

Key characteristics:

• Confident
• Responsible
• Perfectionist
• Selfish