"Illustration in a treatise of Phrenology of ", 1873 Charles Bell Illustration in , New York, New York, USA

Formerly, analyses of facial features (Physiognomy or Characterology is now discredited). Enthusiasts exaggerated the possibility to detect mental-psychological characteristics by analyses of facial features. On the other hand, it is self-evident that it is easy to tell what persons have African, Asian, or European facial traits. Clever clinicians who have "trained eyes" can also recognize children and adults with oligophrenia (limited mental capacity). Muscles of facial expression develop further if utilized intensely (expressions of complex emotions, etc.). Oligophrenics often have limited range or unusual facial expressions. Symmetric or partial facial paralyses result in "poker faces", indicative of "lack of expressions".

NOTE. There is a potential confusion concerning the term "Phrenology". In strict sense Phrenology is the study of the human mind (Psyche) and related disorders such as Schizo-phrenia (schizophrenia - split personality), Oligo-phrenia (oligophrenia - lacking mental capacity), etc. The term Phrenology was expropriated by those who claimed to understand the human mind by studying facial features.