Over the last century, common understanding of personality has evolved from anecdotal descriptions of the distinctions of few remarkable people to a robust scientific model that is capable of measuring individual variances in innate traits that are common to everyone. This article provides a brief description of several important developments in the scientific understanding of personality and how it is assessed for individuals.

It has long been observed that the personality (or character) of an individual shapes the way they process information coming in from the world around them as well as how they function independently, interpersonally, and within their greater social communities. Personality represents the innate and persistent thought, feeling, and action tendencies of individuals. Greater understanding of human personality holds the promise to illuminate a common framework of characteristics, how they differ between individuals and manifest in important health, educational, occupational, economic, cognitive, and social outcomes.

Comparing and contrasting the unique personality of individuals is an activity that goes back millennia. Philosophies on moral character and individual virtues have waxed and waned. Beginning in the 20th century, the scientific method was put to the task of exploring the concept of personality in earnest. Interdisciplinary efforts leveraging expert attention in fields such as psychology, linguistics, statistics, and data science to systematically explore innate differences in people’s thoughts, feelings, and actions.

As a result of this collaboration across fields of study and the work of scientists in academic and public sector institutions, a much clearer picture of the nomothetic personality traits that underlie the many facets of how we describe human personality has emerged. In particular, two separate streams of research independently found that personality can be effectively described using five factors.

Beginning in the 1930’s, a lexical stream of research posited that personality is such an important component of culture that its underlying structure is evident from the words used within language (Allport and Odbert, 1936). By systematically analyzing the words used to describe individual differences in personality within various languages, lexical researchers found five underlying factors of personality consistently emerging (Goldberg, 1981).

Separately from the lexical stream of research, a community of personality psychologists developed a variety of personality questionnaires designed for practical use to assess specific constructs. By one count, over 170 different scales were developed between 1900 – 1970 and, despite their variety, many of them measured similar traits (Goldberg, 1971).

In the 1970s-80s, the two streams of research began to coalesce and the lexical theory of five underlying factors was further reinforced by findings from various questionnaire methods and advancements in psychometrics. By the ‘90s, studies comparing self-report with peer and spouse ratings and those demonstrating trait heritability were consistently finding agreement for the same five traits, namely: neuroticism, extraversion, openness, agreeableness, and conscientiousness (McCrae & Costa, 2008).

Since that time, support for the five factor personality model (also known as the ‘Big 5’) has increased through numerous validation studies. As a result, researchers now have a replicable and comprehensive model of personality that can be easily measured across cultures.

Five factor assessments are now regularly applied in clinical, educational, medical, and organizational settings, as well as more broadly to many research domains. This has enabled researchers to explore associations between an individual’s standing on the five factor traits with dozens of important life outcomes such as personal well-being, relationship satisfaction, peer status, and career choices. New findings are continually being discovered, replicated, and validated.

For many years, personality testing was primarily conducted in clinical, research lab, or psychometric settings. In these more controlled environments, the results of personality assessments were carefully processed by expert professionals who could then tailor feedback to subjects based on their particular needs.

More recently, technology has broadened access to online personality assessments. People who have access to the internet are able to participate in a wide variety of active personality research and assessment services, including some that measure traits along the five factors.

Often, an outcome of using online personality assessment tools is a computer-generated report containing a summary of the subject’s statistical standing for each trait and a narrative interpretation of the results, describing how that standing may provide insight into various social tendencies.

The value that users receive from reviewing the assessment interpretation reports will depend on many factors, including the degree to which the user can understand and is familiar with the language, terms, and definitions used in the report; clarity of the scoring methodology and statistical findings; and alignment between any subjective licenses in the narrative with quality research.

Interpreting the results of a personality assessment is inherently a subjective experience. Users will compare and contrast their knowledge of the subject – many times they themselves are the subject – with the information contained in the assessment interpretation report. Assessment providers can provide higher quality interpretation experiences by providing context to the user, explaining terms and definitions, being transparent about how assessments are scored and statistical assumptions built into the results, and building facts and references into their narrative.