The scope (application), reliability, and validity of the method are discussed. It is concluded that "despite the rapid progress in the field, the impressiveness of research and the accumulation of valuable data, the scientific validity of the method is still open to challenge." "Unless objectivity and validity are attained and established, it must become inevitably the discipline of a chosen few." (PsycINFO Database Record (c) 2006 APA, all rights reserved)