Final answer:
The method used to catalog human traits was through psycho-lexical study, collecting a large number of words and categorizing them based on their meaning and relevance to human traits. The word lists used included descriptors for various aspects of human personality, behavior, and physical traits.
Step-by-step explanation:
The method used to catalog around 18,000 human traits was through psycho-lexical study, as described by Allport and Odbert in their 1936 publication on trait-names. They collected a large number of words from dictionaries and other sources and categorized them according to their meaning and relevance to human traits.
The word lists used for this purpose included a wide range of descriptors that captured various aspects of human personality, behavior, and physical traits. These descriptors were organized into categories and dimensions, such as warmth, reasoning, emotional stability, dominance, and many others.