The Mask of Sanity is a book written by Hervey Cleckley, M.D., first published in 1941, describing the clinical interviews of Cleckley with incarcerated psychopaths. It is considered a seminal work and the most influential clinical description of psychopathy in the 20th century. The basic elements of psychopathy outlined by Cleckley are still relevant today.[1] The title refers to the normal "mask" that conceals the mental disorder of the psychopathic person in Cleckley's conceptualization.[2] Cleckley describes the psychopathic person as outwardly a perfect mimic of a normally functioning person, able to mask or disguise the fundamental lack of internal personality structure, an internal chaos that results in repeatedly purposeful destructive behavior, often more self-destructive than destructive to others. Despite the seemingly sincere, intelligent, even charming external presentation, internally the psychopathic person does not have the ability to experience genuine emotions. Cleckley questions whether this mask of sanity is voluntarily assumed intentionally to hide the lack of internal structure, or if the mask hides a serious, but yet unidentified, psychiatric defect.[3] An expanded edition of the book was published in 1982, after the DSM, the manual used in the United States for categorizing psychiatric disorders, had changed the name and standards for the classification of psychopathy to antisocial personality disorder, incorporating most of Cleckley's 16 characteristics of a psychopath listed below.[4] The original edition of the book is no longer available. Cleckley introduced 16 behavioral characteristics of a psychopath: [5] Superficial charm and good intelligence Absence of delusions and other signs of irrational thinking Absence of nervousness or psychoneurotic manifestations Unreliability Untruthfulness and insincerity Lack of remorse and shame Inadequately motivated antisocial behavior Poor judgment and failure to learn by experience Pathologic egocentricity and incapacity for love General poverty in major affective reactions Specific loss of insight Unresponsiveness in general interpersonal relations Fantastic and uninviting behavior with drink and sometimes without Suicide threats rarely carried out Sex life impersonal, trivial, and poorly integrated Failure to follow any life plan.