the first psychological clinic opened in 1896 at the university of pennsylvania by lightner witmer.in the first half of the 20th century, clinical psychology mainly about psychological assessment, not treatment. after world war ii, there was a big increase in the numbers of trained clinical psychologists. there are two main educational models - the ph.d. scientist-practitioner model which looks at research, and the psy.d. practitioner-scholar model which looks at treatment. clinical psychologists are now regarded as experts in psychotherapy.