The personality of individuals defines their behavioral choices, but how exactly the personality traits are expressed remains uncertain, limiting our ability to create a computable model of a personality and predict behaviors. Here, we proposed a new functional personality model that is based on modern neuroscience advances and defined by four parameters: 1) The hedonic values assigned to different “pleasant” aspects of behavioral outcomes (homeostatic balances, improved social status, et cetera); 2) The aversive values of ”unpleasant” aspects (loss of sexual opportunity, potential of injury, loss of monetary reward, et cetera); 3) Summation parameters: discounting and dissolution parameters for simultaneously processed hedonic/aversive events; and 4) Threshold: the relationship between magnitude of predicted outcome and manifestation of behaviors. We expressed the idea through a mathematical formula, applied it, and at 0.90 power demonstrated that our model has an ability to estimate actual responses (Spearman's Rank-Order correlation = 0.5). Although more research and tuning are needed, we believe that our functional model may eventually allow accurate prediction of human behavior.