1. A method of fitting a hearing assistance device for a user, comprising: presenting to the user using a computer stimulus pairs adapted to provide contrasting options for selection from a set of stimuli stored in the computer; receiving inputs from the user entered into the computer, including preference judgments of the user; calculating a score for each stimulus of the pair using the computer to execute a rank agreement function to maximize agreement between scores and the preference judgments; selecting a set of genes based on the scores, wherein the set of genes correspond to hearing assistance device parameters; operating on the set of genes with a genetic algorithm using the assigned scores to obtain a child set of genes; and determining in which order to present various stimulus pairs from the set of stimuli to the user for paired preference judgments, by minimizing degrees of distance between elements of various possible stimulus pairs, wherein the child set is used to provide parameter values during fitting of the hearing assistance device.