Washington

Legos haven’t become astronomically expensive in the past 35 years — a new international study says the popular kids’ toy has also developed a bit of an attitude problem.

Lego characters released since the early 1990s are proportionately more angry, the study found. Authors of the study hypothesized that the spike in negativity could be related to the release of more thematic Lego sets — such as pirates or “Harry Potter” — that include weapons, along with miniature figurines representing “good guys” and “bad guys.”

“It is our impression that the themes have been increasingly based on conflicts,” wrote researchers Christoph Bartneck, Mohammad Obaid and Karolina Zawieska. Two of the authors work for the University of Canterbury, New Zealand; the third is from the Industrial Research Institute for Automation and Measurements in Warsaw.

Researchers arrived at this conclusion through a scientific process that can read as almost comical. After cataloguing and photographing the 3,655 Lego characters released between 1975 and 2010, the researchers asked 264 American adults to characterize the figures’ expressions as angry, happy, sad, disgusted, surprised or fearful.

Bartneck, who will present the paper on his findings at the First International Conference on Human-Agent Interaction in Sapporo, found a proportional growth of angry faces since the early 1990s. Variables such as skin color and whether the figure’s head is attached to a body didn’t substantially throw off their conclusions.

That may be alarming for some in a world where chewing a Pop-Tart into a gun shape is grounds for school suspension — as a Maryland boy learned in the spring — and the psychological effect of violent video games remains hotly debated. One would predict that conflict-oriented figurines are the last thing parents want in their kids’ toy chests. In fact, the researchers themselves sounded concerned about the implications for child psychology, saying: “We cannot help but wonder how the move from only positive faces to an increasing number of negative faces impacts how children play. . . . The children that grow up with Lego today will remember not only smileys, but also anger and fear in the minifigures’ faces.”

But before you confiscate your kids’ Legos, consider the good that even angry Legos can do. The study’s authors said that a range of emotional expressions connect “to the complex interaction scenarios of today’s users.” In other words, the variation mirrors reality, in which anger, fear and “smileys” all magically coexist. And some child psychologists have suggested that conflict-driven games, even those with toy weapons, help kids grapple with issues like “the struggle between good and evil,” a point made by George Washington University’s Jonathan Turley in a controversial 2011 opinion piece in the newspaper USA Today.

Lego does still sell boring old building blocks. They may lack flashy movie tie-ins — “Hobbit” Legos, anyone? — but experts agree they are still great for kids.