If you want to look at how a toy evolves over time, Legos are probably your best bet.

It’s the largest toy manufacturer in the world, for one. It has its own movie and theme parks, as well as books and video games that supplement its iconic building block sets. Plus, it’s been making those bricks since 1949, allowing the researchers to trace the evolution of a single genre of toy over decades.

“There are very few toys that have been continuously on the market,” Christoph Bartneck, a professor at the University of Canterbury in New Zealand, told me in an email. “One could try to take a sample of all toys each year, but that would be difficult. Lego products are extremely well-documented.”

In a new study published in PLOS One, Bartneck and his colleagues sifted through that documentation and found that Lego toys have had “significant exponential increases of violence over time.”

They analyzed the violence of Legos in two ways. One, by looking at “weapons bricks”—how many were released each year, the proportion of weapons bricks to non-weapons bricks, and the proportion of sets that included weapons. (They got this data from BrickLink.com, which has “the exact inventory of every brick in every set the Lego company released since 1949,” the study says. Thank goodness for collectors.) And two, by having people look at Lego catalogs, which show the sets fully constructed, as they’re intended to be used, and asking them to note all the instances of violence they saw.

Lego first included weapons in its Castle set in 1978—“a sword, a halberd, and a lance,” the study says. Since then, the proportion of sets that included weapons increased by an average of 7.6 percent annually.

The proportion of weapon bricks to non-weapon bricks got several boosts over the years—from Pirates sets, introduced in 1989, which brought handguns and cannons into the mix, as well as from the Bionicle sets, introduced in 2005 and 2006. Bionicle is an original Lego creation, set in a science-fiction universe, the storyline of which, if Wikipedia is any indication, is head-swimmingly complex. But there were a lot of weapons involved, it seems. (The introduction of Star Wars sets did not seem to have an effect on these trends, but the researchers note that may be because other weapon-heavy sets were discontinued around the same time, or because the design of this study doesn’t count weapons like the Death Star that you build out of multiple normal bricks.)

There was a notable decrease in the proportion of sets with weapons in 2001, which the study speculates may be because the Lego Group had some financial difficulties that year. But overall, the trend has been toward more and more weapons, and in 2014, nearly 30 percent of sets included weapons.


Lego Weapons Pieces and Sets Over Time

PLOS One

The sets as displayed in the catalogs also got rowdier, with an average 19 percent annual increase of displays of any kind of physical violence. There was also an average 11.7 percent increase of “nonverbal psychological aggression” which included perceived instances of “forcing, subjection … intimidation, violating one’s human rights … and scorning gestures.”

The increased violence in Lego sets is particularly interesting because Lego used to advertise itself as an alternative to violent toys. A Lego ad from 1966 blares the word “Peace” in giant script across the top of an image of two children harmoniously playing with the little blocks. “There is, in this nervous world, one toy that does not shoot or go boom or bang or rat-a-tat-tat,” the ad reads. “Its name is Lego. It makes things.”

And it still makes things—it’s just that some of the things it makes might inspire kids to say “bang.” Perhaps this eventual acquiescence to violence is just a matter of Lego having to stay competitive in an entertainment environment where violence abounds.

“In the ‘80s you had the upsurge of action figure toys with which Lego had to compete,” says Gary Cross, a professor of history at Pennsylvania State University who has studied toys and children’s culture. “Also with video games, when Nintendo comes in and Sega and the rest of them in the 90s, that obliged Lego to make accommodations. It’s a big company. They have all of these people; they have to give them retirements and healthcare and whatnot, so they’re adapting to the culture that has been effectively shaped by other toy companies. I’m not defending them, I’m saying that’s the context in which they’ve operated.”

Lego sets, which are often based on other entertainment franchises, may also just be a reflection of the violence elsewhere in pop culture. The children demand Star Wars toys, and Star Wars is violent.

In the new study, the researchers suggest that toy manufacturers may be “locked in a metaphorical arms race for exciting new products,” and “exciting” may sometimes mean “violent.” But it also notes that compared to other similar toys, Lego “could still be considered to be relatively mild.” Mega Bloks, for instance, has building sets based on Call of Duty and Halo, some of which are straight-up tanks. K’nex has one called “Combat Crew” which includes a drone.

And the company still says it opposes violence, and that toys depicting realistic warfare is a line they will not cross. “We see a clear distinction between conflict and violence,” Amanda Santoro, a brand manager for Lego, told me in an email. “And we do not make products that promote or encourage violence. Weapon-like elements in a Lego set are part of a fantasy/imaginary setting, and not a realistic daily-life scenario.”

There is a rich debate (and by “rich” I mean “contentious and confusing”) about what effect, if any, violent play could have on children. There is research that says that playing with toy guns increases anti-social behavior, and research that says aggressive play is helpful for child development.

Regardless, “I do believe that children will adopt play themes with guns and weapons, in spite of the fact that most adults would prefer they not,” Jeffrey Trawick-Smith, a professor of early childhood education at Eastern Connecticut State University, told me in an email. “One of my play research mentors, Brian Sutton-Smith … once commented that children are going to play violent themes, as long as there is violence in our society. If we could only end the violence on the streets, on TV, in the movies, maybe we could end the violent play.”

Bartneck’s suggestion: “Buy the bricks, toss the instruction and build your own models. A brick is just a brick and you can play with it in whatever way you want.”