Some debates have pervaded the field of psychology since its genesis. Perhaps one of the most salient ones deals with the nature of personality. Personality psychology studies one's distinctive style of cognition, behavior, and affect. However, this concept elicits discord among psychologists as some have insisted that it does not exist, while others struggle with issues of measurement. Some debates have pervaded the field of psychology since its genesis. Perhaps one of the most salient ones deals with the nature of personality. Personality psychology studies one's distinctive style of cognition, behavior, and affect. However, this concept elicits discord among psychologists as some have insisted that it does not exist, while others struggle with issues of measurement. Personality, one's characteristic way of feeling, behaving and thinking, is often conceptualized as a person's standing on each Big Five personality trait (extraversion, neuroticism, openness to experience, agreeableness and conscientiousness). A person's personality profile is thus gauged from their standing on five broad concepts which predict, among other life outcomes, behavior and the quality of interpersonal relationships. Initially, it was believed that one's Big Five profile was static and dichotomous in that one was either at one extreme of each trait or another For example, people are typically categorized as introverted or extraverted. Personality was therefore assessed in terms of generalities or averages. In noticing the strong inconsistencies in how people behaved across situations, some psychologists dismissed personality as nonexistent. This school of thought attributes human behavior to environmental factors, relegating individual differences to situational artifacts and contesting the existence of individual predispositions. It was led by situationists like Walter Mischel (1968). Their contention held that personality was a fictitious concept. For them, the discrepancies observed across one's behaviors were evidence that interindividual differences did not exist Some aspects of the situationist perspective even suggest that all human beings are the same and that the differences we observe are simply illusory biproducts of the environment. However, personologists soon integrated these inconsistencies into their conceptualization of personality. They modified the old, more monolithic construct by measuring how people differ across situations. Their new methods of personality assessment describe fluctuations in personality characteristics as consistent and predictable for each person based on the environment he is in and his predispositions. Some work suggests that people can espouse different levels of a personality dimension as the social situations and time of day change Therefore, someone is not conscientious all the time, but can be conscientious at work and a lot less so when she is home. This work also suggests that intrapersonal variations on a trait can be even larger than interpersonal variations. Extraversion varies more within a person than across individuals, for example. This work was based on individual self-ratings during the day across a long period of time. This allowed for researchers to assess moment-to-moment and day to day variations on personality attributes.Personologists now tend to agree that people's personalities are variegated and are not to be conceptualized through bipolar characterizations (e.g. extraversion vs introversion). Rather people oscillate between the two extremes of a trait. The pattern of this oscillation then constitutes personality. In addition, social roles (e.g. employee) have been identified as a potential sources of personality change. Researchers have found strong correspondences between the demands of a social role and one's personality profile. If the role requires that the person enacting it be conscientious, her standing on this trait is more likely to be high. Conversely, once he leaves that role and or takes on another which entails less conscientiousness, he will manifest a lower level standing on that trait. Longitudinal research demonstrates that people's personality trajectories can often be explained by the social roles they espoused and relinquished throughout their life stages. Thus social roles are often studied as fundamental predictors of personality. The goals associated with them elicit the appropriation of certain personality profiles by the people enacting them. For example, employees judged effective by their peers and superiors are often described as conscientious as well. Personality also changes through life stages. This may be due to physiological changes associated with development but also experiences that impact behavior. Adolescence and young adulthood have been found to be prime periods of personality changes, especially in the domains of extraversion and agreeableness. It has long been believed that personality development is shaped by life experiences that intensify the propensities that led individuals to those experiences in the first place, which is known as the corresponsive principle. Subsequent research endeavors have integrated these findings in their methods of investigation. Researchers distinguish between mean level and rank order changes in trait standing during old age. Their study of personality trajectories is thus contingent on time and on age considerations. Mottus, Johnson and Geary (2012) found that instability engendered by aging does not necessarily affect one's standing within an age cohort. Hence, fluctuations and stability coexist so that one changes relative to one's former self but not relative to one's peers. Similarly, other psychologists found that Neuroticism, Extraversion (only in men), and Openness decreased with age after 70, but Conscientiousness and Agreeableness increased with age (the latter only in men). Moreover, they suggest that there is a decline on each trait after the age of 81.