What Science Says About Why Boys Are Fascinated With Trucks

Research suggests that testosterone is the reason boys are fascinated in trains, planes and automobiles. However, stereotypes should not be rules to follow.

“Mama! City bus! Mama, Mama! Big truck! Mama, crane!” shout my boys from their car seats on our way to anywhere.

“I know, buddy. I see it! So cool!” Unless I acknowledge the existence of said vehicles and construction machinery, my almost three year old twin boys will continue to repeat what they saw, even after it is no longer in view.

Diggers in action, trucks hauling cars, and trains moving along the tracks are impressive. But unless I had my toddlers in the car I wouldn’t notice every garbage truck, cement mixer, or tractor. I’m just not into things on wheels. My boys, one much more than the other, are.

My older daughter played with trucks when she was a toddler and still will sometimes, but she never had this obsession. During a recent trip to Costco, where it felt like I was acknowledging every other vehicle on the road, I started to wonder if there’s a scientific reason why boys like trucks. Turns out, there is.

Congratulations! It’s A…First Let’s Talk About Gender

Like most expectant parents, when my partner was pregnant with our children we wanted to know the sex of our babies.

The curiosity was too much and, for me, the knowing seemed like it would be a way to better bond with the baby. Rather than call the baby “it,” I wanted to provide a male or female pronoun to my partner’s growing belly. By the 20 week ultrasound of our first child, we learned we were having a girl. The second pregnancy’s ultrasound revealed that our second and third children were twin boys.

We labeled our children based on their sexual anatomy. And for the most part, sexual anatomy is an indication of gender identity. But the two are very different things and by definition happen through different processes.

We all start life genderless, in regards to sexual anatomy. The last set of our chromosomes make us genetically male (XY) or female (XX) and hormones determine the growth of our sexual organs. Around six weeks in utero, a surge of testosterone will push the fetus toward being male. Without this addition of testosterone, the fetus will become female. Sexual anatomy is locked into place, but gender identity is not.

There are at least fifty genes that shape the development of gender identity.

Later in pregnancy, as the brain develops according to interactions with genes and prenatal exposure to hormones, a child’s innate gender identity will form; again, it will usually match the sexual anatomy that has already formed, but as shown in transgender individuals, this is not always the case. There are at least fifty genes that shape the development of gender identity.

Author of Becoming Nicole, Amy Ellis Nutt, states this when talking about gender identity:

“Gender variance, it seems, is the norm, not the exception, and yet the binary view of male/female and the pathologizing of anything that doesn’t conform to these expectations is stubbornly entrenched.”

Brain Bias

Because of hormones, our brains develop with a bias toward male or female identity—or something in between. External influences and pressures may influence gender expression and the willingness to be open about one’s true gender identity, but our wiring cannot be changed. We are who we are. And much of who we are assumed to be is wrapped up in being labeled male or female.

When my partner and I learned our first child was a girl, I was hesitant to tell our family members and some friends. I didn’t want the onslaught of pink, frilly, and lace covered clothing. I didn’t want nursery decorations that indicated she was a princess and made of sugar and spice and everything nice. The same was true when we found out we were having twin boys. We didn’t want items that assumed boys were rough and tumble.

Telling people our children’s gender based on their sexual anatomy led people to purchases and conversations that over feminized our daughter and over masculinized our sons. Before our children expressed an interest in anything, they were expected to like stereotypical female and male things.

Are We Still Talking About Trucks?

Yes. Because where there is smoke there is fire, i.e., hormones.

Two independent studies in 2002, performed by Gerianne M. Alexander and Melissa Hines, and in 2008, performed by Janice M. Hassett, Erin R. Siebert, and Kim Wallen, showed preferences to toys based on gender using first vervet then the rhesus monkeys. Male monkeys favored toys considered to be for boys (ball, car), while female monkeys were drawn to stereotypical girl toys (baby doll).

The gender neutral toys (book, stuffed dog) were played with equally. The fascinating thing about the studies is that the subjects had no external pressure to play with one toy over the other. They were not under any societal pressure or influence to choose a toy based on what they should because of gender norms and roles.

In fact, they had never seen a car or baby doll before, yet the male monkeys were drawn to the car, pushing it back and forth, while the female monkeys rocked the baby doll and lifted her skirt to see what was hiding underneath.

Monkeys, Gender

Both reactions to the toys are the same as exhibited in curious boys and girls playing with the same types of toys.

Researchers suggest that testosterone is the reason. Children, generally boys, with higher levels of testosterone are drawn to toys labeled as male-typical toys. And girls who are exposed to high levels of the sex hormone androgen while in utero, a condition known as Congenital Adrenal Hyperplasia (CAH), tend to have a male biased brain and are also drawn to male-typical toys.

If The Hormones Fit

Boys will be boys? Not always. It is too easy to conclude that females are predetermined to be more nurturing and social than males, and that males are programmed to be more active.

While evolutionary traits may make girls value social stimuli (faces) more than males do, and males value things that complement their skills at spatial navigation (moving parts), it’s much more involved and complicated than that. And it all goes back to the levels of hormones, specifically testosterone, that we are exposed to in the womb.

Those hormones determine sexual anatomy and gender identity, thus providing male and female cognitive differences that affect the way we learn and make decisions, including the toys we choose as children.

toy-truck2

One very telling finding in the 2008 study was this:

“These data suggest that males show strong preferences for mechanical toys or strong aversion to plush toys, when they are asked to choose between two competing toys presented simultaneously, while females do not show this bias…for toy choice, information processing may be filtered in males. Wheeled toys command attention and their perceptual characteristics overshadow information coming from plush toys. Females do not filter information in this fashion, thus all toys are equally interesting.”

Stereotypes may exist for a reason, but they should not be rules to follow.

A truck can make a boy happy and a doll can make a girl happy. But the same can also be said for the opposite scenario.

We should diversify the activities, toys, and colors we show our children because, if given the chance, it is likely they will show variations outside of what some consider gender normal. As he or she ages, there is a possibility that a child’s choice of toy is based on what is expected of them in order to appease a parent or society instead of his or her built-in, biological desire.

One of my sons prefers toys that are considered female-typical toys, yet he will still play with balls and cars. My other son seems to follow all of the stereotypes applied to boys. He’s very active. He’s rough. He loves trucks, trains, and motorcycles.

If those are not around, a baby doll will do. But it is not unlikely that the baby will be turned into a weapon, ball, or something to pounce on. This behavior was not taught by me or his other mother, or even from kids at school since he is home full-time with me and his gentler brother. My sons’ behaviors and obsession—or lack thereof—with fast and loud objects are likely a direct result of the amount of testosterone flowing through their bodies.