When the great architect Philip Johnson first visited the Guggenheim Museum in Bilbao , designed by Frank Gehry, he started to cry. “Architecture is not about words. It’s about tears,” Johnson reportedly said . Something about the museum’s majestic curves moved him at an emotional level. Many others must get a similar feeling, because the building is usually ranked among the most important in modern times.

Whether or not Johnson and Gehry realized it, the Bilbao and its swirling façade tapped into a primal human emotional network. Time and again, when people are asked to choose between an object that’s linear and one that’s curved, they prefer the latter. That goes for watches with circular faces, letters rendered in a curly font, couches with smooth cushions–even dental floss with round packaging.

The Cognitive Neuroscience Laboratory at Harvard Medical School

The Cognitive Neuroscience Laboratory at Harvard Medical School

Recently neuroscientists have shown that this affection for curves isn’t just a matter of personal taste; it’s hard-wired into the brain. Working in tandem with designers in Europe, a research team led by psychologist Oshin Vartanian of the University of Toronto at Scarborough compiled 200 images of interior architecture. Some of the rooms had a round style like this:

Courtesy of Oshin Vartanian

Others had a rectilinear form, like this:

Courtesy of Oshin Vartanian

Vartanian and collaborators slid people into a brain imaging machine, showed them these pictures, and asked them to label each room as “beautiful” or “not beautiful.” In a study published earlier this year, they reported that test participants were far more likely to consider a room beautiful when it was flush with curves rather than full of straight lines. Oblong couches, oval rugs, looping floor patterns–these features got our aesthetic engines going.

It’s worth noting this isn’t a men-love-curves thing; twice as many women as men took part in the study. Roundness seems to be a universal human pleasure.

Beauty ratings were just the first step in the study. The researchers also captured the brain activity that occurred when the study participants in the imaging machine considered the pictures. Turns out people looking at curved design had significantly more activity in a brain area called the anterior cingulate cortex, compared to people who were looking at linear decorations. The ACC has many cognitive functions, but one is especially noteworthy in the context of Vartanian’s study: its involvement in emotion.