Have happy jingles gone the way of tie-dye and the twist? A study of more than 1,000 top-40 tunes from the last five decades finds that music has gotten gloomier since the 1960s (Psychology of Aesthetics, Creativity, and the Arts, 2012).

"Purely happy-sounding things, which are emblematic of children's music, have become less fashionable," says E. Glenn Schellenberg, PhD, a psychologist at the University of Toronto Mississauga, who co-authored the study with Christian von Scheve, PhD, of Freie Universität Berlin.

Over the last half century, the researchers found, pop songs have become slower and minor keys have become more prevalent — both qualities that evoke sadness in Western music. Mixed musical emotions are also more common in modern music, with today's fast-paced dance tunes much more likely to be written in minor keys. "Not all the cues are pointing in the same direction," Schellenberg says. "The music has a more complex emotional structure."

He blames the trend on our increasingly sophisticated society. As our lives and our technology have gotten more complicated, so has our entertainment — we're more often playing high-tech video games instead of reading novels. "I think there's a growing appreciation of complexity in art forms in general," Schellenberg says.

But that may not be the end of the story. In the last year or two, Schellenberg has noticed a re-emergence of happy-sounding music. Major-mode hits such as Madonna's upbeat Give Me All Your Luvin' stand out in a sea of minor-key pop tunes. "Madonna has her finger on the pulse," he says. "I think pop music probably works in cycles, and what once sounded childish now sounds fresh."

—Kirsten Weir