Computer-implemented method for assessing an aging adult's ability to classify formant transition and segment duration information in making phonetic categorizations. A representative subset of multiple confusable pairs of phonemes is selected. A representative subset of multiple stimulus levels for the phonemes is selected for use with the phoneme subset. For each pair of phonemes of the phoneme subset, at each stimulus level of the stimulus level subset: icons for each phoneme are graphically presented, and a computer-generated phoneme from the pair is aurally presenting at the stimulus level. The adult is required to select one of the icons corresponding to the aurally presented phoneme, and the selection's correctness or incorrectness recorded as a response result. A success rate is determined based on the response results, the success rate comprising an estimate of the adult's success rate with respect to the multiple confusable pairs of phonemes at the multiple stimulus levels.