Psychometrics, to a large extent, relies on statistical methods to confirm the validity of psychometric tests. Confirmatory Factor Analysis (CFA) is considered the main tool when structuring the psychometric tests. This reliance on linear statistics, however, inherits the limitations of statistical methods: their incapacity to deal with contingent, nonlinear, interdependent natural systems and their multiple feedback mechanisms. To maximize the content validity of psychological assessment tools, the structure of these tools should be justified by the findings from biological and social sciences. This talk illustrates the benefits of following neuroscience and not factor analysis in structuring the tests that measure biologically-based traits, such as temperament. The studies reported here used a neurochemistry-validated temperament test, the Structure of Temperament Questionnaire (STQ-77) and the Trait Polymathy Scale (TPS), comparing its differential power to the differential power of the Big Five Personality Inventory (BFI), information about educational grades and the Barratt Impulsivity Scales (BIS-11). Results showed that STQ-77Pt provided more subtle differentiation between the Breadth, Depth and Integration components of polymathy than the Big Five model. When compared to estimated and documented schooling grades in adults, there was a distinct activity-specific pattern of correlations with the STQ-77Pt scales.