Baby boys wear blue; baby girls wear pink.
Here are some more: As toddlers, girls love dolls and boys play with fire trucks. As they reach school age, boys are more adventurous, while girls are more sensitive. While these gender stereotypes might seem a little-old fashioned, we can’t deny the power they still have. As parents, we start establishing our kids’ genders as soon as they’re born—often earlier, whether we’re choosing nursery paint or launching balloons at a gender reveal party. 
But from a scientific perspective, parents are likely much more concerned about gender than their kids are. In fact, gender takes a while to set in, and the way that we raise our kids has everything to do with how gender roles are established. How we as parents interact with our children—the toys we give them, the rules we make them follow, even the words we use to describe them—can have far-reaching consequences on the way kids see themselves and the adults they grow up to be. This is, of course, a touchy subject, and it’s easy to misstep. To discuss it accurately, we reached out to Robert W. Blum, MD, professor and director of the Urban Health Institute at Johns Hopkins University and co-author of a recent six-year study focusing on gender expectations and their effect on adolescents all over the world. He spoke with us about what the latest science says about gender and childhood development.
Before we go any further, though, there’s an important distinction to be made. Those already privy to it, bear with us.
Sex isn’t the same thing as gender. The two terms are frequently confused, but in order to understand gender, we need to differentiate it from biological sex. According Vanessa LoBue, PhD, an assistant professor of psychology at Rutgers University, sex is a matter of biology. 
“Each cell in our body has 46 chromosomes. A father’s sperm and a mother’s egg each has only half – 23 each. At conception, the chromosomes of the [mother and father] match up into 22 identical pairs, with the 23rd pair being the sex chromosome,” LoBue wrote in The Conversation. A chromosome can either be an X or a Y, she explains, and “in most cases, XX chromosomes will become female and XY chromosomes will become male,” though as many as 1 in every 50 children are born with a reproductive anatomy that doesn’t fit with the typical definitions of female or male. While sex is about a person’s chromosomal makeup and physical characteristics, gender has more to do with how we relate to ourselves and those around us. 
“Gender is what actually gets expressed – how we look, how we act and how we feel,” LoBue wrote. “While sex is determined by what is written into the chromosomes or what is dictated by our biology, known as genotype, it is the interaction between the genes … and the environment that determines gender.” In other words, both biology and environment play a role in determining a person’s gender—and parents are one of the biggest and most consequential elements of a developing child’s environment. Whether or not we realize it, we’re communicating certain sex-based assumptions and expectations to our children, and those can have profound consequences on their development.
In a sense, gender is a factor from birth—at least as far as parents are concerned.
“We know that young people are exposed to gender roles, gender norms, and gender messages starting in infancy,” Blum tells us. Research going as far back as 1974 shows that parents have different opinions and expectations of newborns based on their sex within 24 hours of birth, even when controlling for weight, length, and Apgar score (a rating of how healthy the newborn is). According to one study’s abstract, “Daughters were significantly more likely than sons to be described as little, beautiful, pretty, and cute, and as resembling their mothers.” 
The emphasis on girls’ physical beauty doesn’t end there, though; for girls across cultures, it becomes a significant psychological burden. According to Kristin Mmari, DrPH, an associate professor at Johns Hopkins Bloomberg School of Public Health who co-authored the study with Blum, “In New Dehli, the girls talked about their bodies as a big risk that needs to be covered up, while in Baltimore girls told us their primary asset was their bodies and they need to look appealing—but not too appealing.” More recently, a 2016 study showed that unfamiliar adults presented with recordings of babies’ cries made assumptions of a given child’s sex based on the idea that adult women’s voices are higher than men’s. Babies with higher-pitched cries were assumed to be female and babies with lower-pitched cries were assumed to be male. 
The same study showed that there is no significant difference between the cries of both sexes—the adults were making assumptions. More importantly, these assumptions affected the adults’ perception of the infants’ gender attributes. The participants rated the higher-pitched cries as “expressing more discomfort” than the cries from the lower-pitched babies. Interestingly, in both studies, the judgements of the adult men were more heavily based in gender stereotypes than those of the adult women. These assumptions about the connections between sex, gender, and pain, also continue to manifest themselves later in life. While the connections between the three are enormously complex, a growing body of work indicates that observed differences between males’ and females’ dealing with pain are likely influenced by assumptions and expectations connected to gender. 
According to a recent review of clinical and experimental findings on the subject, “Gender roles have been associated with pain response, with the masculine gender norm dictating increased tolerance of pain among males, whereas feminine gender norms accept pain as a normal part of life and are more permissive of pain expression.”
For children, reactions to gender messages and expectations seem to come in waves.
“As children, we start out thinking more flexibly about gender than we end up,” LoBue wrote. Infants can use gender labels early in their development (25 percent use gender labels in 17 months, while 68 percent use labels by 21 months), but at a very rudimentary level. Children typically don’t develop an awareness of their own “selves” until they’re around 18 months old. 
Though many parents’ treatment of their children is affected by gender stereotypes almost from the moment of birth, LoBue says, “In my own research, I’ve found that children don’t begin to notice and adopt gender-stereotyped behaviors (e.g., preferring colors like pink or blue) until the age of two or three.” According to LoBue’s research, children don’t believe in gender permanence prior to age 5. Preschoolers will frequently ask their mothers whether they were little boys when they were younger, for example, or a young girl might say that she’ll grow up to be a daddy. 
A 1989 study by psychologist Sandra Lipsitz Bem illustrates that point quite effectively. Bem showed preschool-aged children three photographs of two toddlers: one male and one female. The first photo showed the toddler without clothes, while the second showed the same toddler in stereotypically-gendered clothing corresponding to their sex. The third photo showed the toddler dressed in stereotypically-gendered clothing corresponding to the opposite sex. Initially, Bem showed the preschoolers the first photo alongside the second and asked them whether the toddler was a boy or girl. The results were obvious; the children’s responses matched both the biological sex and stereotypically-gendered clothing. However, when Bem presented the preschoolers with the third photo alongside the first, the majority changed their response—if their first answer was “boy,” they said the toddler was now a girl. Only the preschoolers who believed that genitalia is the essence of boy-ness or girl-ness correctly identified the toddlers, while the rest seemed to focus on the clothing one wears as a more important element of what it is to be a boy or girl. 
The study indicates that children have a fluid concept of gender around that age; they believed that the same toddler had changed from a boy to a girl (or vice versa) based on the clothing in which the toddler was dressed. Between ages 3 and 5 (when children begin to see gender as permanent), however, they begin to prefer playing with gendered toys (trucks as opposed to dolls, for instance) and with children of the same gender, according to a 1999 study cited by LoBue. But gender can also become more fluid around ages 7 to 9, then solidify again when kids are in classrooms on a regular basis. Their environment likely plays a role; teachers, for instance, often segregate children based on gender for classroom activities. Children learn to self segregate—for instance, the boys begin to sit separately from girls during lunchtime—and kids who cross these boundaries risk being teased. 
So, are genders fairly set in stone by middle childhood? Not quite.
When it comes to gender, puberty is enormously important.
“These gender norms tend to become more solidified—they become hard to change around the age of 14 or 15,” Blum tells us. “Around puberty, as children transition from looking like children to looking like teenagers or adults, they get messages from everyone around them about what is appropriate for a girl to do and a boy to do.”
Boys fight more, they drink more … [Girls’] social worlds shrink—literally shrink.
“The messages they receive are variations on a theme known as the Hegemonic Myth: the myth that boys are strong, girls are weak; boys are competent, girls are incompetent,” Blum says. “There are a whole set of associated messages. Girls get the message, every place they look, that they now are sexual beings … Girls when they start going into puberty are seen as the physical manifestation of … sensuality.” 
On the other hand, Blum says that boys don’t get the same treatment. Instead, they’re taught that they have the right to exert their “power” and “dominance” over others. “Boys don’t get that message,” he says. “Boys get the message that they’re strong and … powerful.” Parents often reinforce these stereotypes in a variety of ways—daughters tend to have earlier curfews than sons, and are less likely to get permission to use the family car; they’re also more likely to be given chores at home, while their male counterparts are given chores away from home. 
These “gender-discriminatory beliefs,” he says, “have profound health consequences.” The result? “Boys fight more, they drink more … ,” Blum says, “[and they perish] more due to interpersonal violence and this physical assertiveness.” “[Girls’] social worlds shrink—literally shrink,” he continues. “They don’t go out, they don’t have as broad a social network. [Gender roles] limit girls’ education, they lead to early marriage [and contribute to] gender-based violence and early pregnancy.”
So what should parents do to encourage healthier development?
Blum says he sees the solution as simple—though not necessarily easy.
We have come a long way in 50 years, so I see what’s possible.
“We teach—in our schools, in our churches, in our homes—that personal respect is the core expectation of how people relate,” he says of the solution. “We teach tolerance, and we teach respect, and we simply don’t allow the language of disparity or gender discrimination or the behaviors of it.” In other words, empathy is key. Parents, and society, should respect how gender develops, rather than force kids into strict categories that they might not fit into. More concretely, parents should make sure that they aren’t projecting gender-based assumptions and expectations on their children. “Never stereotype children’s traits such as boys are loud and noisy, girls are calm and sweet, and call out relatives and teachers who do so,” said child and adolescent therapist Katie Hurley to CNN. “Monitor your own interactions with boys and girls, and comfort a boy as you would a girl if they are sad or unhappy.” 
Hurley also emphasized that parents must take every opportunity to cultivate their child’s awareness of restrictive gender messages, discussing and correcting gender-based assumptions they encounter, saying, “Let’s break apart the media. Let’s poke the holes. Let’s say princesses aren’t real.” Breaking down restrictive gender stereotypes won’t be easy, but Blum remains optimistic, pointing to increases in awareness surrounding things like child abuse, spousal abuse, and bullying. “We have come a long way in 50 years, so I see what’s possible,” he says. “I see these changes as very feasible.”
