In 1980, all the figurines that came in sets of interlocking bricks were “smileys” — with seemingly sunny personalities to match their bright yellow visages.

But in the mid-1990s, only about 80 percent of figurines were putting on a happy face, and by 2010, the proportion had dropped to 50 percent, the researchers found. …

They plotted the emotions — happiness, anger, fear, disgust, surprise and sadness — on a time chart to illustrate how the two-inch toys have gotten crankier with the passing years. By 2010, about 30 percent of the figurines were hot under their removable collars. …

“We cannot help but wonder how the move from only positive faces to an increasing number of negative faces impacts how children play,” Bartneck wrote in his study.