Alex Jensen had noticed that his 14-year-old daughter and 9-year-old son were bickering more often than usual lately. On a recent morning, while father and daughter were on an outing together, the teen turned to her dad and shared her perspective about the dynamic between her parents and brother.

“She said, ‘I’m just so annoyed that you guys always take his side,’ ” Jensen recalled.

It was the type of accusation that might make many parents feel a reflexive, defensive urge - to immediately say no, we don’t, or that’s not true. Instead, Jensen said: “Okay - how?”

“She said, “Well, every time he’s doing something annoying, you tell me to ‘just ignore him,’ and that really drives me crazy,’ ” he said.

Jensen was uniquely able to understand the importance of this moment: An associate professor in the school of family life at Brigham Young University, he is the lead author of a recent study, published by the American Psychological Association, that examined parental differential treatment and which children are more likely to receive it. The study found that gender, birth order and a child’s temperament can shape whether a child is favored by their parents.

In Jensen’s family, there was a justifiable explanation for why the siblings were being treated differently - the gap in maturity between a 14-year-old and a 9-year-old, which his daughter understood as they talked about it - but the episode illustrates why a child might feel like there is a favored sibling, he said. And the implications of those feelings can be significant.

The idea of parental favoritism might seem inherently subjective (what do we mean by “favorite,” exactly?) but researchers have developed ways to identify differences in the ways parents treat their children, Jensen said.

“Very few studies are going to approach parents and say, ‘Well, who is your favorite child?’ Parents aren’t going to answer that. They’re going to say, ‘I don’t have one,’ ” he says. Instead, researchers asked parents for more concrete information: Does a parent experience more conflict with a particular child? With which child does a parent spend more time? Is there a child who typically receives more affection? More financial investment? More help with homework?

Similar questions are also posed to children, he said: “We’d ask the kids: Compared to your sibling, who does your parent spend more time with?”

The findings of the study indicated some clear and consistent patterns: Daughters tend to be favored by parents - according to parents themselves; children didn’t report that same pattern from their perspective, Jensen said.

“That one was surprising,” he said. “There are a couple of older studies that suggested that fathers are going to favor sons, and mothers are going to favor daughters, so that’s what we were expecting to find - but it turns out fathers favor daughters, too.”

There were also some benefits to being an older child, the study found: “Older siblings were given more freedom and more autonomy,” Jensen said. At first glance, that might seem intuitive; older children are typically more mature and responsible. “But we’re also looking to see if there’s a change between childhood, teen years, adulthood, and we found it doesn't matter,” he said. “Even as adults, parents still give more freedom to their older kids.”

More predictably, the study also found that certain personality traits are linked to favored treatment: Children who were agreeable (“a kid who is compliant, where a parent asks them to do something and they’re more likely to do it,” Jensen said) and conscientious (“kids who are more aware and more responsible,” he said) also tend to be favored by parents.

The study, a meta-analysis of existing research, included 30 studies as well as 14 unpublished datasets about parental differential treatment, Jensen noted, representing more than 19,000 participants from across North America and Western Europe.

This information is important, Jensen noted, because “there are decades of research showing that the kids who tend to get the less-favored treatment tend to have poorer outcomes.” They are more likely to be depressed or anxious, he said, and more likely to get in trouble at school or engage in substance use as teens. “One study suggested they are less likely to go to college, and less satisfied with their life as adults,” he said. For the children who are favored, the reverse is true, he noted: Research shows that they have better mental health, less trouble at school and are more likely to go to college.

By identifying the children most likely to experience these effects, Jensen’s findings might be of particular value to therapists, social workers or clinicians who support families, said Megan Gilligan, an associate professor in the department of human development and family science at the University of Missouri who has studied sibling relationships. Parental differential treatment not only shapes the bond between parent and child, she said, but between siblings as well.

“We sometimes forget about the sibling relationship, or we make assumptions about it, but being aware of those sibling dynamics and how they play a role is important,” she said.

The sibling relationship is especially salient in adolescence, she said, and research has shown that those childhood dynamics “do set the stage for later life”: If parental differential treatment affects the sibling bond, the impact can carry through into their adult relationship.

But it’s also important to recognize that some degree of parental favoritism is far more widespread than we might want to admit, she said.

“For the families experiencing this, it feels really personal, and it feels unique to their individual family,” Gilligan said. “But it’s happening in most families. We’ve been able to document it from early childhood all the way to when folks are into their 60s, and still perceive differential treatment or favoritism from parents. It’s not just something that happens when we’re kids.” If more people understand that this phenomenon is common, she says, it might help them feel more able to acknowledge the family dynamics in their own households. “It might help them feel less defensive,” she said.

Jensen echoed that notion. “Every parent is going to treat their kids differently, so parents shouldn’t take a study like this and say: ‘Oh, shoot, I treat my kids differently, I’ve messed up.’ I don’t want parents to have that takeaway - but rather, just recognize that sometimes differences in treatment can be problematic.”

If parents take an opportunity to reflect honestly on how they interact with their children, he said, it can help make those dynamics feel more comfortable to everyone involved.

“There are some studies that suggest that two things need to happen: One, the differences in treatment need to be legitimate” - for instance, he said, a parent might need to spend more time with a sibling who requires extra academic support or has special medical needs - “and the siblings need to understand that. So even if you feel it’s legitimate, if the kids don’t understand that and don’t buy into that, it could still have these negative effects.”

But if a child does understand why a parent might need to focus more on a sibling, those negative impacts are mitigated, Jensen said. “So parents should start there: ‘Why do I treat my kids differently? Is there something legitimate about that?’ ”

If there’s an uptick in conflicts between siblings, or if a child says outright that they think something is unfair, “then I think as a parent, you need to be willing to listen to why they feel that way,” he says. “Not just saying, ‘hey, you’re wrong, this is okay because of X, Y and Z - but actually be open to having conversations with your kids about this.”

One thing he definitely doesn’t want, Jensen said, is for his study to add another layer of parental guilt.

“I’ve had this conversation with hundreds, maybe thousands of people, with friends and family and parents and students, and I get this sense that a lot of parents end up feeling really guilty. I don’t have a solution for that, really, but - guilt doesn’t do good things in families,” he said. “We all make mistakes as parents. So, focus on improvement, but try to leave the guilt behind.”