How to measure the personality.

Among the personality traits that describe enduring differences between people, the Eysenck dimensions of neuroticism versus psychoticism and extraversion versus introversion are the most distinct. Based on factor analysis, these personality traits are referred to as the big two. Attempts to describe more factors, such as in the so-called five-factor personality model, have up till now not been successful from a measurement point of view.

Using item response theory models to evaluate the Eysenck personality traits from a measurement point of view in terms of scalability have confirmed that questionnaires covering neuroticism, psychoticism, extraversion, or introversion are most adequate in measuring personality.