The increase in angry faces among Lego mini figures is a sign of the times, says the author of a new study on the toys.
The faces of the figures have changed, reflecting a growing focus on conflict in the popular construction toy, said robot expert Dr Christof Bartneck from the University of Canterbury.
The faces of Lego figures, which were previously all smiling, now included a range of emotions, and a high proportion of angry faces.
"When I grew up the only thing I ever had was smiley faces, and I had very positive and happy memory of Lego," he said.
"If you go into a toy store these days what you see is that a lot of the themes and topics, particularly for the toys for the boys, are very rich in conflict and war and weapons.
"It seems to be a sign of the times that this is currently what is popular in toys and what sells," he said.
Dr Bartneck said the scientific community was still debating the impact of violence in games and toys, but there was clearly a shift towards conflict themes.
"Playing conflict is not necessarily a bad thing. A super-duper happy world where everybody always smiles is probably not desirable either."
Dr Bartneck has published catalogues of all 6000 figures released to date. His paper on Lego facial expressions involved photographing the 3655 figures released between 1975 and 2010.
He said while Lego figures in the 1970s all had the same smiley face, from 1989 the range expanded to include hundreds of different emotions.
Different skin colours from the standard Lego yellow were also introduced.
For the study, samples of the faces were shown to 264 participants, who described the emotion and its intensity.
Dr Bartneck said the faces could be grouped into six main clusters: disdain, confidence, concern, fear, happiness and anger. Angry and happy expressions were the most common.
Dr Bartneck said Lego had an overall positive impact on child development, such as helping with spatial understanding and fantasy development. "It's a wonderful toy for that and I think it has for that sense a very positive effect."
Dr Bartneck is the head of UC's HIT lab, which focuses on human interface technology, and will present his findings at the First International Conference on Human-Agent Interaction in Sapporo, Japan on August 7.
Otago University psychology professor Jamin Halberstadt said it was interesting that the study found how Lego faces were perceived was influenced by their context.
He said this was borne out by studies on human facial recognition as well.
On the other hand, how the Lego characters were perceived was not influenced by changing the figure's skin colour.
"It's also kind of interesting that there's such a rich emotional life of Lego," he said.
"People are always seeing faces in all sorts of things, so there's already a bias to see faces, and it seems like it doesn't take much to get a rich variety of emotions, even from a very simple combination of lines and squiggles."