【A Science-Minded Mom’s Observation Report】 How My Children Came to Understand “Gender”

*“EN-ICHI Partners” are contributing authors who provide articles to EN-ICHI from their respective fields of expertise.

As a mother of three and a science researcher, I find children's growth to be like a grand research theme integrated into everyday life. Physical development, cognitive formation, psychological processes—the way these advanced functions develop naturally through daily life and interactions, without being taught by anyone, is always moving to witness. What was particularly impressive was the process by which

my childrencame to recognize "gender." Recently, there has been a boom in sex education, and "sex education at home" has suddenly become commonplace, and I myself have become more conscious of wanting to "actively convey what needs to be said about sex to my children as a parent." On the other hand, I have also had more opportunities to hear the idea that "gender is not just male and female" and "masculinity and femininity are unconscious biases," and I have sometimes found myself wondering "how should I explain the terms male and female to my children?" With

such questions in the back of my mind, I have objectively observed the growth of my three children with the eyes of a science-minded mother, and I have come to feel that there are some commonalities in the process of recognizing "gender." While this is just one family's case, I'd like to compile an observation report of my children in the hope that it might serve as a useful resource for thinking about better "sex education."

The Moment They Noticed “Gender”

My eldest son first showed a clear interest in "gender" when his sister (my eldest daughter) was born. At the time, he was just under three years old. He was just old enough to have everyday conversations, and he was fascinated by the newborn baby he was seeing up close for the first time, and he took part in taking care of her. While changing diapers together many times, one day he suddenly asked this question: "Did you (his name) not have a penis when you were little?" It was so unexpected that I still remember almost laughing. He probably combined the information that: - His sister doesn't have what I do - His sister is "small" - I am "big" with this information and formed his own hypothesis that "People are born without a penis, and develop one as they grow." As a three-year-old, he was observing the differences between himself and others and trying to inductively derive a rule that seemed to apply. I was amazed by his thought process, even as a researcher. Later, when he saw my body in the bath, he said, "Oh, Mom, you don't have a penis either . " It was the moment when his hypothesis, which he had tested by applying it to a different subject, completely fell apart. So I replied, "Mommy doesn't have it, but what about Daddy?" and he immediately constructed a new hypothesis, saying, "Daddy does! Oh, so boys have it!" He arrived at an answer that explained all the observable facts at that moment, and he looked satisfied. I think this experience was the first time he connected the words "boy" and "girl" with his own physical characteristics.

The “Need to Confirm” Phase

From then on, around the age of four or five, my eldest son often said things like:
"I'm a boy, Daddy's a man, Mommy's a woman, and my sister's a girl."
"Is [friend's name] a boy?"
"Is [teacher's name] a woman?"
He would repeatedly confirm the gender of people close to him and try to establish his criteria for distinguishing them, as if an AI were learning data.

Then, around the age of six,
while choosing a birthday present on his smartphone, he casually said,
"This is a girly toy, so it might be good for [sister's name]'s birthday."
Up until then, I myself had hardly ever used the expressions "boyish" or "girly," so it was a very surprising moment for me.

*Photo for illustrative purposes only

My Daughter: An Urge to Classify

My eldest daughter also went through a phase around the age of five where she loved categorizing things as "boys" or "girls." She

was more of a verbalizer than her brother, and on the back of the bicycle on the way to daycare in the mornings, she would endlessly ponder things like,
"Mommy and I have long hair, so we're girls,"
"Big brother and Daddy have short hair
"But Ms. So-and-so is a girl, but she has short hair, doesn't she?
sister has short hair too.

" "I, So-and-so, and So-and-so are girls, so we like pink," she
All I could do was listen to her "data learning" in full swing.

Even When We Tried to Be Careful

Personally, I had always wanted to avoid imposing rigid stereotypes on my children. Influenced by the idea that expressions like “masculine” and “feminine” reflect adult biases, I had tried not to use such language.

It's the same at the nursery school my child attends; I rarely hear comments like, "She's so cute and girly." When she says things like , "It has frills!" or "She likes pink!" , the natural response is a neutral one that accepts the child's perspective without associating it with gender, such as, "You really like frills, don't you?" or "You really like pink, don't you?"

They acknowledged the child’s perspective without linking it to gender. And yet, despite these efforts, children naturally tried to understand what “boys” and “girls” meant. Watching this, I gradually came to feel:

"Perhaps children themselves have a desire to understand the concept of 'gender' as part of the process of understanding themselves and others."

An Innate Drive to Learn

This feeling was inspired by the Montessori concept of "self-education."

Montessori education is a famous educational philosophy advocated by a female physician named Maria Montessori, characterized by its systematization based on thorough observation. A central value is the belief that children themselves possess an inherent "self-education" that leads to independence and development.

For example,
children ask the names of everything they see, such as: asking "What's this?", "What's this?", "What's this?", etc.;
wanting to touch food directly with their hands
; climbing and jumping over
any steps; noticing even slight changes in the usual order or place
; and easily memorizing meaningless sequences of letters and numbers

. Anyone who has experience raising children will likely relate to these behaviors. In Montessori education, these behaviors are seen as expressions of the child's own spontaneous "self-education"—the desire to develop this ability right now.

Furthermore, because these behaviors are commonly observed at certain periods, there are considered to be "sensitive periods for development." The book defines nine skills—language, sensory, motor skills, order, small objects, numbers, writing, reading, and culture/manners—and defines periods in which children spontaneously strive to develop each of these skills. The educational approach proposed is that during these sensitive periods, adults should not overly restrict such behaviors, but rather create a safe environment where children can fully test and develop these skills. I have

seen this firsthand many times with my own three children. When they say, "I really want to do this now," instead of prioritizing my own convenience and trying to cut them off with a quick fix, if I wait for them to do it to their satisfaction as much as possible, they move on to the next thing with surprising ease. This has made me keenly aware that there are indeed such things as "sensitive periods for development."

*Photo for illustrative purposes only

A Desire to Grasp “Gender”

Furthermore, the way my eldest son and daughter showed a strong interest in "gender" around the ages of 2 to 6 seemed very similar to what I observed. I began to think that this level of effort to grasp the differences between "boys" and "girls" is an expression of children's spontaneous self-educational ability to grasp "the essence of the attribute of the gender they were born with" and to try to understand themselves more deeply, and that it would not be an exaggeration to call it a "sensitive period for gender."

In Montessori education, there is no definition of a "sensitive period for gender" in the "sensitive periods for development." However, it is defined thatwithin the "sensitive period for sensation," there are two stages:anaccumulation period (0-3 years old) in which children perceive things around them with their five senses,andan organization and classification period (3-6 years old) in which they compare and classify identical things based on the sensory impressions they have made during that period. The behavior of my children around the ages of 2 to 6seemed to fit perfectly as "a period in which they perceive and accumulate physical and individual characteristics they see around them with their five senses, and are sensitive to comparing, classifying, and characterizing identical things in terms of 'gender'."

If you think about it,
penises, poop, farts—
babies become surprisingly fascinated by them from around the age of two. They
're not actively taught about them by anyone, yet they're intensely drawn to them for some reason. This coincides with Freud's developmental stages: the anal stage (around 1-3 years old) and the phallic stage (around 3-5 years old).

A “Sensitive Period for Gender” as a Developmental Stage

There may be a developmental stage around ages two to six—a kind of "sensitive period for gender.”

What do parents raising children think about this perspective?

When I talk to other mothers about this kind of behavior at this stage, I often get a lot of empathy, so I feel like there might be quite a few similar stories out there. On the other hand, I don't see much detailed verbalization of the process of recognizing one's own gender in academic fields such as developmental psychology.

Perhaps this is because it's a behavior that is easily seen in everyday family life, where children have opportunities to see physical differences and express their thoughts frankly, and therefore it hasn't been a subject of research.

Invitation to Participate in a Reader Survey

Therefore, we have decided to conduct a reader survey for those of you who are reading this column.

[EN-ICHI Reader Survey: Call for Parenting Observation Reports!]

If you have any memories of children you know who showed interest in gender or who talked about gender, please share them using the form above. We also welcome any memories of your own childhood experiences. We would like to use your

responses to write a new article for EN-ICHI. Like Maria Montessori, we hope to gain deeper insights into the developmental stages of gender cognition based on numerous observations, so we would greatly appreciate your cooperation.

Reference materials

• Minna no Omochabako (Everyone's Toy Box) "The Basics of Montessori Education! A Chart of Sensitive Periods"https://minna-no-omochabako.com/montessori-sensitive-periods-chart/　(Last accessed April 13, 2026)
• National Center for Child Health and Development (2025) "Revised 2nd Edition Manual for Physical Examinations in Infants and Toddlers"https://www.ncchd.go.jp/center/activity/kokoro_jigyo/shinsatsu_manual.pdf　(Last accessed April 13, 2026)

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