Whether it’s because of intelligence, charisma or physical attractiveness, it’s no secret that some parents favour one child over another.

If you have siblings, you’ve likely witnessed the undeniable favouritism seen in families and perhaps even been a preferred child yourself.

However, a parent’s clear and systematic preference of one child over another can have far-reaching effects.

Mike Levine, ArtSci ’12, said though he hasn’t breached the subject of favouritism with his parents, it’s been a reoccurring theme throughout his life.

His 18-year-old sister Amanda is the favourite because of her musical talents, he said.

“My sister’s a really good opera singer, and I’m not good at literally anything,” he said. “Whenever guests are over they always show videos of her singing or on YouTube … It’s all about her opera talent.”

However, Levine said picking favourites seems natural.

“I think it’s really hard not,” he said. “As a kid, you feel like you favour your dad or your mom, and it’s just as hard with parents as it is as a kid. It’s inevitable.”

A 2005 study from the University of California Davis followed almost 400 families for three years, conducting a total of nine interviews with each set of parents and their children.

After asking them questions and videotaping family interactions, the study concluded that, “65 per cent of mothers and 70 per cent of fathers exhibited a preference for one child, usually the older one.”

Social Darwinism can point to biological reasons for parents’ favoritism. According to a Sept. 22 article in Time Magazine, Time journalist Jeffrey Kluger argues that just like in the animal kingdom, parents are biologically inclined to favour their biggest and healthiest offspring.

These children are seen as the most capable of replicating the family’s genes in future generations.

Queen’s professor of developmental psychology Beth Kelley said parent favouritism can take factors such as physical attractiveness and personality into account.

“There’s research that shows parents pay more attention to their more attractive children, which is kind of scary,” Kelley said. “Parents often bond easier with children who have the same temperament as themselves.”

Favouritism often occurs in families where parents have children from a previous marriage, she said.

“In step families, parents clearly unfavour or favour children. Parents could favour their biological children over step-children even though they try consciously not to,” she said.

Parental favouritism isn’t always intentional.

“Parents adapt their behaviour to what they think meets the child’s needs. Some kids need more supervision, encouragement or structure and rules than others,” she said. “Some kids could misinterpret this as favouring.”

It’s difficult to find an objective way to measure how parents treats their children, because each individual interprets the parent-child relationship differently, Kelley said.

“We see how our parents treat us through the lens of all our experiences and relationships, and how we’ve been treated by our friends and romantic partners,” she said.

Perceived favouritism can provoke sibling rivalry as brothers and sisters compete for their parents’ affection.

In addition, academic achievement is potentially affected by favouritism, Kelly said.

“Certainly the feeling of being loved and valued is related to self esteem and self esteem is related to academic motivation,” she said. “The better your self esteem is, the more empowered you feel to strive to achieve and stick to a difficult task.”

If a child feels favoured by their parents, their other relationships will be affected, Kelley said.

“The relationship one has with their parents and how they feel they’ve been treated is very important,” she said. “Whether you think your parent really loves you and is sensitive to your needs … this is projected on to all your other relationships.

“It’s an internal working model. If you feel your parents didn’t love you as much as your other siblings, you will think other people don’t like you as much as you would like. It’s a self-fulfilling prophecy.”

A study conducted in 2003 by Frank Sulloway at the University of California Berkeley, showed that parental favouritism had a significant effect on personality.

The study found that middle children were less likely than either first-borns or last-borns to report they had been favoured by their parents.

In addition, respondents who said they were favoured by their parents attained higher scores on conscientiousness, and lower scores on openness to experience and neuroticism.

Regardless of perceived favouritism within a household, strong social relationships are built in many ways, Kelley said.

“Parents are not the only people that socialize you,” she said. “Even if you don’t have a great relationship with them, those difficulties can be made up by really good friends, supportive teachers and extended family.”

Kerry Mendelsohn, ArtSci ’13, said she often feels favoured by her parents.

Mendelsohn said she’s typically stronger academically than her brothers.

“When they’re praising you, you feel like you’re favoured in that moment,” she said. “You want to uphold that title almost, I think it’s motivation to succeed and do well.”

Throughout her childhood, Mendelsohn provoked less anger from her parents compared to her two older brothers, she said.

“Being the youngest and being the only girl, I would get yelled at a lot less for similar crimes,” she said. “My dad was a lot rougher when he was mad at the older brothers.”

Favouritism is hard to miss, Mendelsohn said.

“Favouritism is really consolidated and obvious, I think a lot of kids can try too hard to impress their parents, you could feel rejected if you don’t uphold to their standards,” she said.

According to Mendelsohn, both her brothers would disagree that she was the favourite.

“Good parents will make every child feel like they’re the favorite.”

— With files from Katherine Fernandez-Blance