A runway model wears a swimsuit by designer Elie Madi during the Funkshion Miami Swim Week on July 21, 2017. Photo by Gary I Rothstein/UPI | License Photo

Oct. 25 (UPI) -- Men and women are biologically programmed to be drawn to the arched back of a female, new research suggests.

Scientists at the University of Minho in Portugal used 3D models and eye-tracking technology to showcase how slight shifts in posture affect the perception of a woman's attractiveness.


Researchers used computers to generate six 3D models of female upper bodies. Each model featured a slightly different posture, their backs tweaked subtly while still maintaining normal body angles. The models images, pictured from the front, side and the back, were presented to 82 undergraduate students -- a mix of men and women.

The study participants were asked to rate the attractiveness of each model. Both men and women rated the models with their backs more arched as more attractive.

"Increased curvature increases the perception of attractiveness," researcher Farid Pazhoohi said in a news release.

Eye-tracking technology showed both men and women focused their gaze on the rear-view of each model for longer periods of time than on other perspectives. Men tended to focus on the hips, while women trained their eyes on the waist. The link between arched backs and attractiveness was stronger for rear and side-views.

"The latter highlights the unique influence of an arched back on the perception of attractiveness," said Pazhoohi.

The curve in the spine that allows the lower back to bend inward toward the belly is called lordotic posture. Previous studies have showcased the role the posture plays in signaling a female's readiness to mate among a variety of animals, including rats, guinea pigs, sheep, cats, ferrets and primates.

The latest research -- detailed this week in the journal Evolutionary Psychological Science -- suggests the evolutionary signal may also influence human behavior.

"The perception of attractiveness and visual attention to the hip region suggests that lordosis or the arching of the back might signal human females' proceptivity or willingness to be courted," Pazhoohi said. "This also might explain why women wear high heel shoes and why wearing high heel shoes increases womens' attractiveness."