In an article on the method, psychologist Hill Walker, a professor at the University of Oregon who had studied behavioral disorders in schoolchildren for 34 years told Wired Magazine, "There are some serious validity issues here, some reputation-ruining implications." The developers note that Hill Walker has never seen or used a MOSAIC system, and was commenting on the idea or concept, not the actual method. In a letter to the editor following publication of the article, de Becker wrote that MOSAIC for Assessment of Student Threats (MAST) “is the opposite of profiling in that it is always applied to an actual known individual, and it always explores actual behavior and circumstance.