Neuropsychological research on the neural basis of behavior generally posits that brain mechanisms fully suffice to explain all psychologically described phenomena. Terms having intrinsic experiential content (e.g., "feeling," "knowing" and "effort") are not included as causal factors because they are deemed superfluous to the causal mechanisms of brain function. However, principles of quantum physics causally relate mental and physical properties. Use of this causal connection allows neuroscientists and psychologists to more adequately and effectively investigate the neuroplastic mechanisms relevant to the growing number of studies of the capacity of directed attention and mental effort to systematically alter brain function.