The Hidden Self Personality Test app was developed by Dr. Leopold Szondi, a well-known Hungarian psychiatrist and psychotherapist, as a non-verbal personality test to help people discover their inner selves. 

The app is based on his research and work, which was done in the 20th century. In his work, he used various methods to help patients get to know themselves better and to help them discover their personality. He used the photos of psychopaths as a tool to help patients discover their inner drives and characteristics.

The photos in the app are not of ordinary people. They are of patients who were diagnosed with various mental illnesses and were asked to take the test, in order to help the patients discover their inner drives and personalities.