Disclosed herein, among other things, is a method for fitting a hearing assistance device for a user using a genetic algorithm. Stimulus pairs are presented to the user using a computer, the stimulus pairs adapted to provide contrasting options for selection from a set of stimuli stored in the computer. Inputs are received from the user entered into the computer, including preference judgments of the user. A score is calculated for each stimulus of the pair using the computer to execute a rank agreement function to maximize agreement between scores and the preference judgments. A set of genes is selected based on the scores, where the set of genes correspond to hearing assistance device parameters. The set of genes is operated on with a genetic algorithm using the assigned scores to obtain a child set of genes. The child set is used to provide parameter values during fitting.