Editing Trait theory (section)

===Testing methodology, and factors===
Both the EPQ and Big Five approaches extensively use self-report questionnaires. The factors are intended to be [[orthogonal]] (uncorrelated),<ref>{{cite book|author-link=Hans Eysenck|first=Hans|last=Eysenck|year=1990|chapter=Biological dimensions of personality|editor-first=L. A.|editor-last=Pervin|title=Handbook of personality: Theory and research|pages=244–76|location=New York|publisher=Guilford|name-list-style=vanc}}</ref> though there are often small positive [[correlations]] between factors. The five factor model in particular has been criticized for losing the orthogonal structure between factors.<ref>{{multiref2
|1={{cite journal | last1 = Block | first1 = J. | year = 1995 | title = A contrarian view of the five-factor approach to personality description | journal = Psychological Bulletin | volume = 117 | issue = 2| pages = 187–215 | doi=10.1037/0033-2909.117.2.187 | pmid=7724687|name-list-style=vanc}}
|2={{cite journal | last1 = Draycott | first1 = S. G. | last2 = Kline | first2 = P. | year = 1995 | title = The Big Three or the Big Five—the EPQ-R vs the NEO-PI: a research note, replication and elaboration | journal = Personality and Individual Differences | volume = 18 | issue = 6| pages = 801–804 | doi=10.1016/0191-8869(95)00010-4|name-list-style=vanc}}
}}</ref> British psychologist [[Hans Eysenck]] has argued that fewer factors are superior to a larger number of partly related ones.<ref>{{cite journal | last1 = Eysenck | first1 = H. J. | year = 1992 | title = A reply to Costa and McCrae. P or A and C: The role of theory | journal = Personality and Individual Differences | volume = 13 | issue = 8| pages = 867–868 | doi=10.1016/0191-8869(92)90003-8|name-list-style=vanc}}</ref> Although these two approaches are comparable because of the use of factor analysis to construct hierarchical taxonomies, they differ in the organization and number of factors.

Whatever the causes, [[psychoticism]] marks the two approaches apart, as the five factor model contains no such trait. Moreover, psychoticism, unlike any of the other factors in either approach, does not fit a [[normal distribution curve]]. Indeed, scores are rarely high, thus skewing a [[normal distribution]].<ref name="Personality traits"/> However, when they are high, there is considerable overlap with psychiatric conditions such as [[Psychopathy|antisocial]] and [[schizoid personality disorder]]s. Similarly, high scorers on [[neuroticism]] are more susceptible to [[sleep]] and [[psychosomatic]] disorders.<ref>{{cite book|author-link1=Hans Eysenck|first1=Hans|last1=Eysenck|first2=S. B. G.|last2=Eysenck|year=1991|title=The Eysenck Personality Questionnaire-Revised|location=Sevenoaks|publisher=Hodder & Stoughton|name-list-style=vanc}}</ref> Five factor approaches can also predict future mental disorders.<ref>{{multiref2
|1={{cite journal | last1 = Costa | first1 = P. T. | last2 = McCrae | first2 = R. R. | year = 1990 | title = Personality disorders and the five factor model of personality | journal = Journal of Personality Disorders | volume = 4 | issue = 4| pages = 362–371 | doi=10.1521/pedi.1990.4.4.362|name-list-style=vanc}}
|2={{cite journal | last1 = Lynam | first1 = D. R. | last2 = Caspi | first2 = A. | last3 = Moffitt | first3 = T. E. | last4 = Raine | first4 = A. | last5 = Loeber | first5 = R. | last6 = Stouthamer-Loeber | first6 = M. | year = 2005 | title = Adolescent psychopathy and the Big Five: Results from two samples | journal = Journal of Abnormal Child Psychology | volume = 33 | issue = 4| pages = 431–443 | doi=10.1007/s10648-005-5724-0| pmid = 16118990 | s2cid = 24240140|name-list-style=vanc}}
}}</ref>