person's psychological state. Using the theory with individuals Graves demonstrated that individuals react more quickly to words associated with their value system than with those associated with others. More recent research has built on this to show differences in neurological activation among those operating from individualistic vs collectivistic stages. While some academic research has been done on assessing the presence of bio-psycho-social coping systems in individuals, Graves did not publish any such tools. He noted: Those who have tried to develop instruments have based them on what people think, do or believe, which is not the proper base for assessment devices. They should be based not on what the person thinks but how s/he thinks, not on what people do or what they believe but how they do what they do, and how they believe that which they do believe. In the time since Graves's death, assessments have been produced by practitioners of Spiral Dynamics, which is built on E-C theory. While some have treated Graves's levels as a "simplistic categorization tool," Graves noted that even a person centralized at a particular level drew only roughly 50% on that level, 25% on the level before it, and 25% on the level after. In his original data, Graves found that about 60% of his subjects were centralized around one level, while 40% were more mixed. A person might operate from different levels at home vs at work or in other contexts, and might change to be centralized at either a later or earlier level depending on their environment. Criticism Graves's primary data set, which produced the CP-B'O' levels, consisted entirely of students taking his "Normal Psychology" course, raising concerns of sampling bias and lack of diverse life perspectives. During the 1970s, Graves collected additional data from prison populations, industrial workers, and other educational institutions, although it is not documented how this compared to his original methodology, or the degree to which it impacted the theory. Furthermore, the BO and AN levels were the result of research in anthropological literature and therefore not the product of the same methodology as the other levels. Validating Graves's results is viewed as challenging as his raw data was thrown out towards the end of his life, with only collated results retained. Graves's results as presented in his posthumous writing have been criticized as too vague to support the universality of his conclusions. Graves's approach of