The Screening of Passengers by Observation Techniques (SPOT) program, installed by the TSA in 2007, trains screeners to recognize behavioral indicators — like fear or stress — that can be used to identify persons who might pose a risk to aviation security. Those who exhibit those indicators are subjected to additional security screening.

But according to the GAO report released on Wednesday, there’s no evidence that the estimated 3,000 “behavior detection officers” at 176 U.S. airports are actually improving airport security.

“Available evidence does not support whether behavioral indicators can be used to identify persons who may pose a risk to aviation security,” the report said. “The human ability to accurately identify deceptive behavior based on behavioral indicators is the same as or slightly better than chance.”