Agreeableness is a tendency to be pleasant and accommodating in social situations. In contemporary personality psychology, agreeableness is one of the five major dimensions of personality structure, reflecting individual differences in concern for cooperation and social harmony. People who score high on this dimension are empathetic, considerate, friendly, generous, and helpful. They also have an optimistic view of human nature. They tend to believe that most people are honest, decent, and trustworthy.
People scoring low on agreeableness place self-interest above getting along with others. They are generally less concerned with others' well-being, report less empathy, and are therefore less likely to go out of their way to help others. Their skepticism about other people's motives may cause them to be suspicious and unfriendly. People very low on agreeableness have a tendency to be manipulative in their social relationships. They are more likely to compete than to cooperate.
Agreeableness is considered to be a superordinate trait, meaning that it is a grouping of more specific personality traits that cluster together statistically. There are exceptions, but in general, people who are concerned about others also tend to cooperate with them, help them out, and trust them. This dimension of personality was initially discovered in research using the method of factor analysis.
Agreeableness is an asset in a wide range of social situations. Agreeable individuals are biased toward liking others and viewing them in a positive light, whereas disagreeable people are more negative. Despite the label, there is no evidence that those high on agreeableness are more conforming, or influenced by others in making choices, than are their peers.
Because agreeable children are more sensitive to the needs and perspectives of others, they are less likely to suffer from social rejection. Specifically, the research indicates that children who are less disruptive, less aggressive, and more skilled at entering play groups are more likely to gain acceptance by their peers.
One study found that people high in agreeableness are more emotionally responsive in social situations. This effect was measured on both self-report questionnaires and physiological measures, and offers evidence that extraversion and neuroticism are not the only Big Five personality factors that influence emotion. The effect was especially pronounced among women.
The research also shows that people high in agreeableness are more likely to control negative emotions like anger in conflict situations. Those who are high in agreeableness are more likely to use constructive tactics when in conflict with others, whereas people low in agreeableness are more likely to use coercive tactics. They are also more willing to give ground to their adversary and may "lose" arguments with people who are less agreeable. From their perspective, they have not really lost an argument as much as maintained a congenial relationship with another person.
A central feature of agreeableness is its positive association with altruism and helping behavior. Across situations, people who are high in agreeableness are more likely to report an interest and involvement with helping others. Experiments have shown that whereas most people are likely to help their own kin, or when empathy has been aroused, agreeable people are likely to help even when these conditions are not present. In other words, agreeable people appear to be "traited for helping" and do not need any other motivations.
While agreeable individuals are habitually likely to help others, disagreeable people may be more likely to harm them. Researchers have found that low levels of agreeableness are associated with hostile thoughts and aggression in adolescents, as well as poor social adjustment. People low in agreeableness are also more likely to be prejudiced against stigmatized groups such as the overweight.
When mental illness is present, low agreeableness may be associated with narcissistic and anti-social tendencies. In theory, individuals who are extremely high in agreeableness are at risk for problems of dependency, but empirical studies show that many more problems are associated with low agreeableness.
In the United States, midwesterners and southerners tend to have higher average scores on agreeableness than people living in other regions. According to researchers, the top ten most agreeable states are North Dakota, Minnesota, Mississippi, Utah, Wisconsin, Tennessee, North Carolina, Georgia, Oklahoma, and Nebraska.  These findings are consistent with well known expressions in these states, such as "southern hospitality" and "Minnesota nice." Because these states are generally less urbanized than the east and west coasts, people may be more likely to live in small communities and know their neighbors, and consequently, more willing to care about them and help them out.
Friendliness is a characteristic of or befitting a friend; showing friendship: a friendly greeting etc