Agreeableness is a personality trait manifesting itself in individual behavioral characteristics that are perceived as kind, sympathetic, cooperative, warm, and considerate. In contemporary personality psychology, agreeableness is one of the five major dimensions of personality structure, reflecting individual differences in cooperation and social harmony. Agreeableness is a personality trait manifesting itself in individual behavioral characteristics that are perceived as kind, sympathetic, cooperative, warm, and considerate. In contemporary personality psychology, agreeableness is one of the five major dimensions of personality structure, reflecting individual differences in cooperation and social harmony. People who score high on this dimension are empathetic and altruistic, while a low agreeableness score relates to selfish behavior and a lack of empathy. Those who score very low on agreeableness show signs of dark triad behavior such as manipulation and competing with others rather than cooperating. Agreeableness is considered to be a superordinate trait, meaning that it is a grouping of personality sub-traits that cluster together statistically. The lower-level traits, or facets, grouped under agreeableness are: trust, straightforwardness, altruism, compliance, modesty, and tender-mindedness. Like all Big Five personality traits, the roots of the modern concept of agreeableness can be traced to a 1936 study by Gordon Allport and Henry S. Odbert. Seven years later, Raymond Cattell published a cluster analysis of the thousands of personality-related words identified by Allport and Odbert. The clusters identified in this study served as a foundation for Cattell's further attempts to identify fundamental, universal, human personality factors. He eventually settled on 16 personality factors through the use of factor analysis. Further factor analyses revealed five higher-order, or 'global', factors to encompass these 16. Although labelled 'independence' by Cattell, a global factor defined by high scores on the E, H, L, and Q1 factors of the 16PF Questionnaire was an early precursor to the modern concept of agreeableness. Extent of agreeableness in the five factor model of personality is most commonly assessed through self-report measures, although peer-reports and third-party observation can also be used. Self-report measures are either lexical or based on statements. Which measure of either type is used is determined by an assessment of psychometric properties and the time and space constraints of the research being undertaken. Lexical measures use individual adjectives that reflect agreeableness or disagreeableness traits, such as sympathetic, cooperative, warm, considerate, harsh, unkind, rude. Words representing disagreeableness are reverse coded. Goldberg (1992) developed a 20-word measure as part of his 100-word Big Five markers, and Saucier (1994) developed a briefer 8-word measure as part of his 40-word mini-markers. Thompson (2008) systematically revised and improved these markers to develop a 40-word measure with better psychometric properties in both American and non-American populations, the International English Mini-Markers. This brief measure has good internal consistency reliabilities and other validity for assessing agreeableness and other five factor personality dimensions, both within and, especially, without American populations. Internal consistency reliability of the Agreeableness measure for native English-speakers is reported as .86, that for non-native English-speakers is .80. Statement measures tend to comprise more words, and hence consume more research instrument space, than lexical measures. Respondents are asked the extent to which they, for example, Am on good terms with nearly everyone, Am not interested in other people's problems or Sympathize with others' feelings. Cattell's factor analytic approach, used to identify the universal personality structures, inspired countless studies in the decades following the introduction of the 16PF. Using Cattell's original clusters, the 16 Personality Factors, and original data, multiple researchers independently developed a five factor model of personality over this period. From the early 1960s on, these explorations typically included a factor called 'agreeableness' or 'sociability.' Despite repeated replications of five stable personality factors following Cattell's pioneering work, this framework only began to dominate personality research in the early 1980s with the work of Lewis Goldberg. Using lexical studies similar to those of Allport and Odbert, Goldberg chose the term 'Big Five' to reflect the sheer number of personality-related terms encompassed by each of these five distinct factors. One of these, agreeableness, was defined by a number of personality-related words similar to those present in earlier and more recent manifestations of the construct; examples include 'friendly,' 'good-natured,' 'cooperative,' 'trustful,' 'nurturing,' 'sociable,' and 'considerate.' Beginning in the 1970s, Paul Costa and Robert McCrae began researching the development of personality assessments based on factor models. Beginning with cluster analyses of Cattell's 16 Personality Factors, Costa and McCrae initially settled on a three-factor model of personality. These three factors were neuroticism (vs. emotional stability), extraversion (vs. introversion), and openness (vs. closedness) to experience, resulting in the acronym 'NEO.' Due to similarities between their three-factor NEO Personality Inventory and Goldberg's Big Five, Costa and McCrae began to develop scales to assess agreeableness and conscientiousness in the early 1980s. This work culminated in the 1985 publication of the first NEO PI Manual to be based on the full Five Factor Model. Although this marked the introduction of agreeableness to the NEO PI, Costa and McCrae worked for an additional seven years to identify and elaborate on the facets comprising this factor in the Revised NEO Personality Inventory.