EN
The article explores structural distortions of the researcher’s personality (contaminations and exclusions) as one of the causes of his/her diagnostic mistakes. Integrated personality of a diagnostician is an important factor which can prevent making mistakes. Such personality allows for the verification of one’s judgements and hypotheses, offers the possibility to revise one’s achievements, and successfully deal with stereotypes or superstitions. The author postulates incorporating development and formation of desirable personality traits in diagnosticians’ vocational training.