We’ve all seen beauty claims in magazines that promise to give us “better skin in just two weeks” or to “dramatically reduce the appearance of fine lines and wrinkles.”

But many women are not convinced. A new study found fewer than one out of five of such claims was considered truthful by a panel of readers — and ads that used scientific language to describe the benefits were even less persuasive.

Researchers at Valdosta State University in Georgia and the University of Nebraska-Lincoln analyzed 289 makeup, hair care, fragrance and skin care advertisements from April 2013 issues of seven fashion magazines including Vogue, Marie Claire and Glamour.

The claims were divided into categories such as scientific claims like “clinically proven” and endorsement claims like “dermatologists recommend.” Three female judges with varying levels of knowledge about the cosmetics industry sorted these claims into four categories: outright lie, omission, vague