Zuckerman argued that basic factors have a biological-evolutionary basis as evidenced by comparable traits in non-human species, biological markers, and moderate heritability.
[1] The model was developed by administering research participants a large number of pre-existing personality questionnaires and subjecting the results to factor analysis.
A self-report measure called the Zuckerman-Kuhlman Personality Questionnaire, Form III, Revised (ZKPQ) has been developed to assess these five traits.
Zuckerman and colleagues noted that Activity is subsumed under extraversion in some models of personality but argued that it should be considered an independent dimension of temperament that is distinct from sociability.
Reward dependence had a moderate positive association with sociability, and modest negative correlations with Agg-Host and ImpSS.
Self-directedness was negatively correlated with N-Anx and to a lesser extent Agg-Host, and had a moderate positive association with Activity.
[1] Zuckerman stated that the personality factors in the alternative five model have an evolutionary basis and can be identified in non-human species but this is not the case for openness.
The decision by Zuckerman and colleagues to deliberately omit markers of openness to experience from their analysis was strongly criticised by Costa and McCrae, proponents of the five factor model (FFM).