Towards the Non-Self-Reported Assessment of the Dark Traits 20 Years Later: A Systematic Review.

Self-report has historically been considered the "gold standard" for personality assessment due to its widespread use. However, its use has been questioned in recent years, especially in contexts such as forensic psychology, due to measurement biases. The purpose of this study was to systematically identify and categorize non-self-report-based instruments used to assess the Dark Tetrad traits or constructs empirically or theoretically associated with them. A systematic review was conducted in PubMed, PsycInfo, Web of Science, and Scopus databases, and 189 studies were included, which reported more than 250 tools. To obtain a joint view of the results, a classification into 6 categories was proposed following Ortner's and Proyer's classification and adding two more categories after reviewing the literature, called Objective Personality Measures (OPMs). These results provide authors with a wide range of tools they could include in their studies to obtain more reliable results when dealing with self-report biases because the best assessment will always combine different measurement methods. Therefore, researchers are encouraged to continue using in their studies the non-self-report-based tools collected in this review, to continue designing new ones, and to provide more validity results.