Agreeableness, defined as being warm, generous and helpful, increased the most during the 30s. Neuroticism and extraversion declined for women as they aged, but not for men. Openness declined for both men and women as they aged.
As every parent knows, even infants come with a built-in personality. So are humans predisposed to act in certain ways, and believe certain things, even before they know how to read and write?
A fascinating study published in the Association for Psychological Science on June 22 found that different parts of the human brain vary from person to person, and those differences correspond to their personalities.
The researchers, at the University of Minnesota, zeroed in on the so-called Big Five personality traits - conscientiousness, extraversion, neuroticism, agreeableness, and openness/intellect. For the study, 116 volunteers described their personality in a questionnaire and then submitted to a brain scan.
Conscientious people tended to have a bigger lateral prefrontal cortex, a region of the brain involved in planning and controlling behavior, according to lead author Collin DeYoung. They found similar brain differences for neuroticism and agreeableness, but there was no clear difference in brain structure for openness/intellect.
Brain scans also allowed researchers at Harvard University and the University of Aberdeen to conclude in 2006 that different sections of the brain are involved in deciding whether another person is like, or unlike, ourselves. The researchers theorized that the neural machinery might contribute to prejudice because it facilitates perceiving other racial or ethnic groups as different, and it's convenient to think of different as inferior.
One way to fight that, they added, is to emphasize how alike different groups are, rather than how different. All this suggests that human prejudices are deeply embedded - or at least facilitated - by the structure of the human brain. And so is personality.
The Stanford researchers conclude, as do others, that human personality is not fixed and remains "basically a bundle of possibilities that wait to be developed and cultivated."
If so, the students were right in their willingness to confront someone voicing prejudice, if the offender is capable of change. The alternative is to remain silent, and that, too, can have consequences. The Stanford psychologists begin their report with a quote from Martin Luther King.
"Our lives begin to end the moment we become silent about things that matter."