Many psychologists consider Machiavellianism to be essentially indistinguishable from psychopathy, as they both share manipulative tendencies, disregard for morality, and cold callousness as their primary attributes.[93][94] There is an immense and ongoing debate amongst researchers as to whether or not Machiavellianism and psychopathy should be treated as the same construct, or at least treat Machiavellianism as a subset of psychopathy.[95] When tested, High Machs scored consistently high on measures of psychopathy, more than Low Machs. Primary psychopaths also scored higher on the Machiavellianism scale than secondary psychopaths.[96] According to John McHoskey, the MACH-IV test is merely "a global measure of psychopathy in noninstitutionalized populations", and that this is a result of the disconnect between clinical and personality psychology.[88] Many have stated that the Machiavellianism scale measures nothing more than "successful" psychopathy, or psychopathy without the extreme clinical characteristics.[97] Even compared to other "dark" traits, research has shown that Psychopathy correlates with Machiavellianism far more than it correlates with narcissism.[94][98] Some authors have stated that Machiavellianism and psychopathy represent the issue of a jangle fallacy, as both constructs are named differently yet describe the same concept.[99] A recent paper published in 2022 stated that Machiavellianism "is theoretically distinct from psychopathy, but empirically they are nearly indistinguishable".[100] Beverly Fehr even suggested that psychopaths may be simply "High Machs who have had run up against the law".[101] Robert Hare, author of the Psychopathy Checklist, stated that Machiavellianism is more closely related to PCL Factor 1, affective detachment, than to Factor 2, an antisocial lifestyle.[102] According to Christopher Patrick, high Psychopathy Checklist scores correlated with much higher Machiavellianism scores, as well as higher scores on boldness and aggressiveness.[103]
Researchers note that Machiavellianism is well represented in every measure of psychopathy, such as the Factor 1 characteristics on the Psychopathy Checklist, more specifically traits such as "conning/manipulative", "pathological lying,” "callous/lack of empathy", and “glibness/superficial charm”.[104][105][106][101] Donald Lynam and others noted that Machiavellianism is also represented in the "Interpersonal Manipulation" factor in Hare's Self-Report Psychopathy Scale-III and in the "Manipulation" scale in the Elemental Psychopathy Assessment. The researchers state that "ultimately, measures of psychopathy and MACH appear to be measuring the same construct, and MACH assessments fail to capture the construct as articulated in theoretical descriptions".[104] Michael Levenson, author of the Levenson Self-Report Psychopathy Scale, disagreed with the notion of distinguishing machiavellianism from psychopathy, stating that it "does not accord" with empirical research which shows Machiavellianism being heavily related to primary psychopathy.[107] Machiavellianism has a strong relationship with both primary and secondary psychopathy on Levenson's self report test.[108] In experiments High Machs also scored highly on the Psychopathic Deviate subscale on the MMPI.[75][109][110] On the Psychopathic Personality Inventory, created by Scott Lilienfeld and Brian Andrews, there is even a subscale similarly named "Machiavellian Egocentricity".[111][112] The subscale is said to assess a "ruthless and self centered willingness to exploit others".[112][113] Machiavellianism and psychopathy have both been negatively correlated with the recognition of facial emotions, with one study stating that "if the ability to recognise facial expressions is exclusively an affective empathy task, it indeed accounts for the facial recognition deficits found in primary psychopathy and Machiavellianism."[114] High scores on the Triarchic Psychopathy Measure questionnaire strongly correlated with Machiavellianism.[115] One group of researchers noted that by definition, "the interpersonal features of psychopathy involve a calculating, cunning, and manipulative style" thus a highly psychopathic person is ipso facto also a person high on Machiavellianism.[116]
Machiavellianism and psychopathy overlap so heavily that researchers have proposed merging the two traits into each other, preferably incorporating Machiavellianism into psychopathy.[105] There have been attempts to combine Machiavellianism and psychopathy into one construct, such as the creation of a "Dark Dyad" as opposed to a "Dark Triad", with the exclusion of narcissism.[117][118]
A recent study done on criminal psychopaths noted that Machiavellianism showed the strongest association with the affective aspect of psychopathy.[119]