The positive correlation between cooperativeness and CSF volume was the other statistically significant finding in the present study. Although the correlation is potentially interesting, there are some aspects, which should be noted in the interpretation of the result. First, the direction of the correlation can be considered paradoxical since low cooperativeness is considered a risk factor for a personality disorder, and the correlation suggests a link between small relative brain volume and high cooperativeness. Second, the correlation between cooperativeness and CSF was significant only after correction for age and sex. The effect of age, even in the present sample of relatively narrow age range, was clearly the most significant factor in explaining global and regional CSF volume, and any other variables have a minor impact on CSF volume. Third, and most importantly, the range of values should be considered. Although there was a large range of CSF volumes in the study, most subjects scored high in cooperativeness, making a correlation less meaningful (Fig. 4b). It is possible that the relatively small differences of cooperativeness scores in normal subjects have little impact on behavior. For self-transcendence, the raw values of the sample were evenly distributed over the whole range of possible values.