Lexical hypothesis

The lexical hypothesis (also the fundamental lexical hypothesis,lexical approach, or sedimentation hypothesis) is one of the most widely used hypothesis in personality psychology. Despite some variation in its definition and application, the Lexical hypothesis is generally defined by two postulates. The first states that those personality characteristics that are most important in peoples' lives will eventually become a part of their language. The second follows from the first, stating that more important personality characteristics are more likely to be encoded into language as a single word. With origins in the late 19th century, use of the lexical hypothesis began to flourish in English and German psychology in the early 20th century. The lexical hypothesis is a major foundation of the Big Five personality traits, the HEXACO model of personality structure and the 16PF Questionnaire and has been used to study the structure of personality traits in a number of cultural and linguistic settings.

Sir Francis Galton was one of the first scientists to apply the lexical hypothesis to the study of personality, stating:

I tried to gain an idea of the number of the more conspicuous aspects of the character by counting in an appropriate dictionary the words used to express them... I examined many pages of its index here and there as samples of the whole, and estimated that it contained fully one thousand words expressive of character, each of which has a separate shade of meaning, while each shares a large part of its meaning with some of the rest.

Despite Galton's early ventures into the lexical study of personality, over two decades passed before English-language scholars continued his work. A 1910 study by G. E. Partridge listed approximately 750 English adjectives used to describe mental states, while a 1926 study of Webster's New International Dictionary by M. L. Perkins provided an estimate of 3,000 such terms. These early explorations and estimates were not limited to the English-speaking world, with philosopher and psychologist Ludwig Klages stating in 1929 that the German language contains approximately 4,000 words to describe inner states.

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