The Five-Factor or "Big Five" model of personality is arguably the most popular way of describing and conceptualising adult personality. The acronym OCEAN is sometimes used to help remember the five dimensions (Openness, Conscientiousness, Extraversion, Agreeableness, and Neuroticism). This way of describing and understanding personality has evolved from the broader trait approach, and shares common ground with other approaches, such as Eysenck's PEN model (which incorporates Psychoticism, Extraversion and Neuroticism). The strongest proponents of the five factor model are Paul Costa and Robert McCrae, and the measurement of the "Big Five" has become virtually synonymous with the use of the NEO-PI-R questionnaire.